Can you split explode a field in a MySQL query

Question

I have to create a report on some student completions  The students each belong to one client  Here are the tables  simplified for this question    CREATE TABLE   clients       clientId  int 10  unsigned NOT NULL auto increment     clientName  varchar 100  NOT NULL default        courseNames  varchar 255  NOT NULL default        The courseNames field holds a comma-delimited string of course names  eg  AB01 AB02 AB03   CREATE TABLE   clientenrols       clientEnrolId  int 10  unsigned NOT NULL auto increment     studentId  int 10  unsigned NOT NULL default  0      courseId  tinyint 3  unsigned NOT NULL default  0      The courseId field here is the index of the course name in the clients courseNames field  So  if the client s courseNames are  AB01 AB02 AB03   and the courseId of the enrolment is 2  then the student is in AB03   Is there a way that I can do a single select on these tables that includes the course name  Keep in mind that there will be students from different clients  and hence have different course names  not all of which are sequential eg   NW01 NW03    Basically  if I could split that field and return a single element from the resulting array  that would be what I m looking for  Here s what I mean in magical pseudocode   SELECT e  studentId   SPLIT      c  courseNames   e  courseId   FROM

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Here s how you do it for SQL Server  Someone else can translate it to MySQL  Parsing CSV Values Into Multiple Rows   SELECT Author   NullIf SubString       Phrase         ID   CharIndex             Phrase         ID  - ID        AS Word  FROM Tally  Quotes  WHERE ID  lt   Len       Phrase        AND SubString       Phrase         ID - 1  1         AND CharIndex             Phrase         ID  - ID  gt  0   The idea is to cross join to a predefined table Tally which contains integer 1 through 8000  or whatever big enough number  and run SubString to find the right  word  position

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If you need get table from string with delimiters   SET  str    function1 function2 function3 function4 aaa bbbb nnnnn   SET  delimeter        SET  sql statement   CONCAT  SELECT                      REPLACE  str   delimeter      UNION ALL SELECT                              SELECT  sql statement  SELECT  function1  UNION ALL SELECT  function2  UNION ALL SELECT  function3  UNION ALL SELECT  function4  UNION ALL SELECT  aaa  UNION ALL SELECT  bbbb  UNION ALL SELECT  nnnnn

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Here s what I ve got so far  found it on the page Ben Alpert mentioned    SELECT REPLACE      SUBSTRING          SUBSTRING INDEX c  courseNames        e  courseId    1            LENGTH SUBSTRING INDEX c  courseNames        e  courseId           1                       FROM  clients  c INNER JOIN  clientenrols  e USING   clientId

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You can do this with JSON in more recent MySQL versions  It s a blast  We will have a quick preparation to create a numbers table  Then first we create an intermediary table to convert the comma delimited strings into a json array then we will use json extract to blast them apart  I am encapsulating the strings in quotes carefully escaping existing quotes because I had semicolon separated strings containing commas    So to create the numbers table  hopefully you have more clients than courses  choose an adequately big table if not   CREATE TABLE numbers  n int PRIMARY KEY   INSERT INTO numbers  SELECT  row     row   1 FROM clients JOIN  select  row  0  t2    Add LIMIT 50 if you know you only have 50 courses  Now  that was easy  wasn t it  Now on to the real work  honestly it s the quotes that make it uglier but at least it s more generic that way   CREATE TABLE json coursenames  SELECT clientId clientName CONCAT       REPLACE REPLACE courseName                                AS a FROM clients   CREATE TABLE extracted SELECT clientId clientName REPLACE TRIM TRIM     FROM JSON EXTRACT a  concat       n                       FROM json coursenames INNER JOIN numbers ON n  lt  JSON LENGTH a     Wheee   The meat here are these two  the CONCAT       REPLACE coursename                      I dropped the second REPLACE to make it more visible  will convert foo bar bar into  foo   bar   baz   The other trick is JSON EXTRACT a  concat       n       will become JSON EXTRACT a    12   and that s the 13th element in the array  see JSON Path syntax

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Here s how you do it for SQL Server  Someone else can translate it to MySQL  Parsing CSV Values Into Multiple Rows   SELECT Author   NullIf SubString       Phrase         ID   CharIndex             Phrase         ID  - ID        AS Word  FROM Tally  Quotes  WHERE ID  lt   Len       Phrase        AND SubString       Phrase         ID - 1  1         AND CharIndex             Phrase         ID  - ID  gt  0   The idea is to cross join to a predefined table Tally which contains integer 1 through 8000  or whatever big enough number  and run SubString to find the right  word  position

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Building on Alwin Kesler s solution  here s a bit of a more practical real world example   Assuming that the comma separated list is in my table list  and it s a listing of ID s for my other table id  you can do something like   SELECT         FROM      my other table  WHERE       SELECT list FROM my table WHERE id    1234   REGEXP CONCAT       my other table id

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Search in a column containing comma-separated values MySQL has a dedicated function FIND IN SET   that returns field index if the value is found in a string containing comma-separated values  For example  the following statement returns one-based index of value C in string A B C D  SELECT FIND IN SET  C    A B C D   AS result   --------    result    --------         3    --------   If the given value is not found  FIND IN SET   function returns 0  SELECT FIND IN SET  Z    A B C D   AS result   --------    result    --------         0    --------

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If you need get table from string with delimiters   SET  str    function1 function2 function3 function4 aaa bbbb nnnnn   SET  delimeter        SET  sql statement   CONCAT  SELECT                      REPLACE  str   delimeter      UNION ALL SELECT                              SELECT  sql statement  SELECT  function1  UNION ALL SELECT  function2  UNION ALL SELECT  function3  UNION ALL SELECT  function4  UNION ALL SELECT  aaa  UNION ALL SELECT  bbbb  UNION ALL SELECT  nnnnn

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It is possible to explode a string in a MySQL SELECT statement   Firstly generate a series of numbers up to the largest number of delimited values you wish to explode  Either from a table of integers  or by unioning numbers together  The following generates 100 rows giving the values 1 to 100  It can easily be expanded to give larger ranges  add another sub query giving the values 0 to 9 for hundreds - hence giving 0 to 999  etc    SELECT 1   units i   tens i   10 AS aNum FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   This can be cross joined against your table to give you the values  Note that you use SUBSTRING INDEX to get the delimited value up to a certain value  and then use SUBSTRING INDEX to get that value  excluding previous ones   SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name FROM clients CROSS JOIN       SELECT 1   units i   tens i   10 AS aNum  units i   tens i   10 AS aSubscript     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0   As you can see there is a slight issue here that the last delimited value is repeated many times  To get rid of this you need to limit the range of numbers based on how many delimiters there are  This can be done by taking the length of the delimited field and comparing it to the length of the delimited field with the delimiters changed to     to remove them   From this you can get the number of delimiters -  SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name FROM clients INNER JOIN       SELECT 1   units i   tens i   10 AS aNum     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0 ON  1   LENGTH clients courseNames  - LENGTH REPLACE clients courseNames              gt   sub0 aNum   In the original example field you could  for example  count the number of students on each course based on this  Note that I have changed the sub query that gets the range of numbers to bring back 2 numbers  1 is used to determine the course name  as these are based on starting at 1  and the other gets the subscript  as they are based starting at 0    SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name  COUNT clientenrols studentId  FROM clients INNER JOIN       SELECT 1   units i   tens i   10 AS aNum  units i   tens i   10 AS aSubscript     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0 ON  1   LENGTH clients courseNames  - LENGTH REPLACE clients courseNames              gt   sub0 aNum LEFT OUTER JOIN clientenrols ON clientenrols courseId   sub0 aSubscript GROUP BY a course name   As you can see  it is possible but quite messy  And with little opportunity to use indexes it is not going to be efficient  Further the range must cope with the greatest number of delimited values  and works by excluding lots of duplicates  if the max number of delimited values is very large then this will slow things down dramatically  Overall it is generally far better to just properly normalise the database

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It is possible to explode a string in a MySQL SELECT statement   Firstly generate a series of numbers up to the largest number of delimited values you wish to explode  Either from a table of integers  or by unioning numbers together  The following generates 100 rows giving the values 1 to 100  It can easily be expanded to give larger ranges  add another sub query giving the values 0 to 9 for hundreds - hence giving 0 to 999  etc    SELECT 1   units i   tens i   10 AS aNum FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   This can be cross joined against your table to give you the values  Note that you use SUBSTRING INDEX to get the delimited value up to a certain value  and then use SUBSTRING INDEX to get that value  excluding previous ones   SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name FROM clients CROSS JOIN       SELECT 1   units i   tens i   10 AS aNum  units i   tens i   10 AS aSubscript     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0   As you can see there is a slight issue here that the last delimited value is repeated many times  To get rid of this you need to limit the range of numbers based on how many delimiters there are  This can be done by taking the length of the delimited field and comparing it to the length of the delimited field with the delimiters changed to     to remove them   From this you can get the number of delimiters -  SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name FROM clients INNER JOIN       SELECT 1   units i   tens i   10 AS aNum     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0 ON  1   LENGTH clients courseNames  - LENGTH REPLACE clients courseNames              gt   sub0 aNum   In the original example field you could  for example  count the number of students on each course based on this  Note that I have changed the sub query that gets the range of numbers to bring back 2 numbers  1 is used to determine the course name  as these are based on starting at 1  and the other gets the subscript  as they are based starting at 0    SELECT SUBSTRING INDEX SUBSTRING INDEX clients courseNames       sub0 aNum        -1  AS a course name  COUNT clientenrols studentId  FROM clients INNER JOIN       SELECT 1   units i   tens i   10 AS aNum  units i   tens i   10 AS aSubscript     FROM  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  units     CROSS JOIN  SELECT 0 AS i UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9  tens   sub0 ON  1   LENGTH clients courseNames  - LENGTH REPLACE clients courseNames              gt   sub0 aNum LEFT OUTER JOIN clientenrols ON clientenrols courseId   sub0 aSubscript GROUP BY a course name   As you can see  it is possible but quite messy  And with little opportunity to use indexes it is not going to be efficient  Further the range must cope with the greatest number of delimited values  and works by excluding lots of duplicates  if the max number of delimited values is very large then this will slow things down dramatically  Overall it is generally far better to just properly normalise the database

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Search in a column containing comma-separated values MySQL has a dedicated function FIND IN SET   that returns field index if the value is found in a string containing comma-separated values  For example  the following statement returns one-based index of value C in string A B C D  SELECT FIND IN SET  C    A B C D   AS result   --------    result    --------         3    --------   If the given value is not found  FIND IN SET   function returns 0  SELECT FIND IN SET  Z    A B C D   AS result   --------    result    --------         0    --------

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I used the above logic but modified it slightly   My input is of format    apple 100 pinapple 200 orange 300  stored in a variable  updtAdvanceKeyVal  Here is the function block    set  res        set  i   1  set  updtAdvanceKeyVal   updtAdvanceKeyVal   REPEAT    -- set r    replace SUBSTRING SUBSTRING INDEX  updtAdvanceKeyVal        i    --  LENGTH SUBSTRING INDEX  updtAdvanceKeyVal        i -1     1            -- wrapping the function in  replace  function as above causes to cut off a character from  -- the 2nd splitted value if the value is more than 3 characters  Writing it in 2 lines causes no such problem and the output is as expected -- sample output by executing the above function   -- orange 100 -- pi apple 200            strange output         -- tomato 500        set  r    SUBSTRING SUBSTRING INDEX  updtAdvanceKeyVal        i                     LENGTH SUBSTRING INDEX  updtAdvanceKeyVal        i -1     1          set  r   replace  r                 if  r  lt  gt     then                set  key   SUBSTRING INDEX  r      1                 set  val   SUBSTRING INDEX  r      -1                  select  key   val        end if         set  i    i   1        until  r      END REPEAT

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You can create a function for this         Split a string by string  Similar to the php function explode         param VARCHAR 12  delim The boundary string  delimiter      param VARCHAR 255  str The input string     param INT pos The index of the string to return    return VARCHAR 255  The  pos th substring    return VARCHAR 255  Returns the  pos th string created by splitting the str parameter on boundaries formed by the delimiter       example       SELECT SPLIT STRING       one two three four   1         This query        DROP FUNCTION IF EXISTS SPLIT STRING  CREATE FUNCTION SPLIT STRING delim VARCHAR 12   str VARCHAR 255   pos INT  RETURNS VARCHAR 255  DETERMINISTIC RETURN     REPLACE          SUBSTRING              SUBSTRING INDEX str  delim  pos               LENGTH SUBSTRING INDEX str  delim  pos-1     1                    delim              Converting the magical pseudocode to use this  you would have   SELECT e  studentId   SPLIT STRING      c  courseNames   e  courseId   FROM

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Seeing that it s a fairly popular question - the answer is YES   For a column column in table table containing all of your coma separated values   CREATE TEMPORARY TABLE temp  val CHAR 255    SET  S1   CONCAT  INSERT INTO temp  val  VALUES     REPLACE  SELECT GROUP CONCAT  DISTINCT   column   AS data FROM  table                          PREPARE stmt1 FROM  s1  EXECUTE stmt1  SELECT DISTINCT val  FROM temp      Please remember however to not store CSV in your DB    Per  Mark Amery - as this translates coma separated values into an INSERT statement  be careful when running it on unsanitised data    Just to reiterate  please don t store CSV in your DB  this function is meant to translate CSV into sensible DB structure and not to be used anywhere in your code  If you have to use it in production  please rethink your DB structure

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Building on Alwin Kesler s solution  here s a bit of a more practical real world example   Assuming that the comma separated list is in my table list  and it s a listing of ID s for my other table id  you can do something like   SELECT         FROM      my other table  WHERE       SELECT list FROM my table WHERE id    1234   REGEXP CONCAT       my other table id

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Until now  I wanted to keep those comma separated lists in my SQL db - well aware of all warnings   I kept thinking that they have benefits over lookup tables  which provide a way to a normalized data base   After some days of refusing  I ve seen the light    Using lookup tables is NOT causing more code than those ugly string operations when using comma separated values in one field  The lookup table allows for native number formats and is thus NOT bigger than those csv fields  It is SMALLER though  The involved string operations are slim in high level language code  SQL and PHP   but expensive compared to using arrays of integers  Databases are not meant to be human readable  and it is mostly stupid to try to stick to structures due to their readability   direct editability  as I did    In short  there is a reason why there is no native SPLIT   function in MySQL

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SELECT   tab1 std name  tab1 stdCode  tab1 payment    SUBSTRING INDEX tab1 payment       1  as rupees    SUBSTRING tab1 payment  LENGTH SUBSTRING INDEX tab1 payment       1     2 LENGTH SUBSTRING INDEX tab1 payment       2    as date FROM     SELECT DISTINCT     si std name  hfc stdCode      if isnull hfc payDate   concat hfc coutionMoneyIn      year hfc startDtae    -    monthname hfc startDtae    concat hfc payMoney       monthname hfc payDate    -   year hfc payDate    AS payment   FROM hostelfeescollection hfc   INNER JOIN hostelfeecollectmode hfm ON hfc tranId   hfm tranId   INNER JOIN student info 1 si ON si std code   hfc stdCode   WHERE hfc tranId    TRAN-AZZZY69454    AS tab1

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I ve resolved this kind of problem with a regular expression pattern  They tend to be slower than regular queries but it s an easy way to retrieve data in a comma-delimited query column  SELECT    FROM  TABLE  WHERE  field  REGEXP     SEARCHED-VALUE        the greedy question mark helps to search at the beggining or the end of the string   Hope that helps for anyone in the future

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MySQL s only string-splitting function is SUBSTRING INDEX str  delim  count   You can use this  to  for example    Return the item before the first separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        1    --------------------------------------------    SUBSTRING INDEX  foo bar baz qux        1     --------------------------------------------    foo                                           --------------------------------------------  1 row in set  0 00 sec   Return the item after the last separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        -1    ---------------------------------------------    SUBSTRING INDEX  foo bar baz qux        -1     ---------------------------------------------    qux                                            ---------------------------------------------  1 row in set  0 00 sec   Return everything before the third separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        3    --------------------------------------------    SUBSTRING INDEX  foo bar baz qux        3     --------------------------------------------    foo bar baz                                   --------------------------------------------  1 row in set  0 00 sec   Return the second item in a string  by chaining two calls   mysql gt  SELECT SUBSTRING INDEX SUBSTRING INDEX  foo bar baz qux        2        -1    ----------------------------------------------------------------------    SUBSTRING INDEX SUBSTRING INDEX  foo bar baz qux        2        -1     ----------------------------------------------------------------------    bar                                                                     ----------------------------------------------------------------------  1 row in set  0 00 sec     In general  a simple way to get the nth element of a  -separated string  assuming that you know it definitely has at least n elements  is to do   SUBSTRING INDEX SUBSTRING INDEX your string       n        -1     The inner SUBSTRING INDEX call discards the nth separator and everything after it  and then the outer SUBSTRING INDEX call discards everything except the final element that remains   If you want a more robust solution that returns NULL if you ask for an element that doesn t exist  for instance  asking for the 5th element of  a b c d    then you can count the delimiters using REPLACE and then conditionally return NULL using IF     IF      LENGTH your string  - LENGTH REPLACE your string              LENGTH       lt  n - 1      NULL      SUBSTRING INDEX SUBSTRING INDEX your string       n        -1      Of course  this is pretty ugly and hard to understand  So you might want to wrap it in a function   CREATE FUNCTION split string TEXT  delimiter TEXT  n INT  RETURNS TEXT DETERMINISTIC RETURN IF       LENGTH string  - LENGTH REPLACE string  delimiter          LENGTH delimiter   lt  n - 1      NULL      SUBSTRING INDEX SUBSTRING INDEX string  delimiter  n   delimiter  -1       You can then use the function like this   mysql gt  SELECT SPLIT  foo bar baz qux        3    ----------------------------------    SPLIT  foo bar baz qux        3     ----------------------------------    baz                                 ----------------------------------  1 row in set  0 00 sec   mysql gt  SELECT SPLIT  foo bar baz qux        5    ----------------------------------    SPLIT  foo bar baz qux        5     ----------------------------------    NULL                                ----------------------------------  1 row in set  0 00 sec   mysql gt  SELECT SPLIT  foo   bar   baz   qux          2    ------------------------------------------    SPLIT  foo   bar   baz   qux          2     ------------------------------------------    bar                                         ------------------------------------------  1 row in set  0 00 sec

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There s an easier way  have a link table  i e    Table 1  clients  client info  blah blah blah  Table 2  courses  course info  blah blah  Table 3  clientid  courseid  Then do a JOIN and you re off to the races

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Until now  I wanted to keep those comma separated lists in my SQL db - well aware of all warnings   I kept thinking that they have benefits over lookup tables  which provide a way to a normalized data base   After some days of refusing  I ve seen the light    Using lookup tables is NOT causing more code than those ugly string operations when using comma separated values in one field  The lookup table allows for native number formats and is thus NOT bigger than those csv fields  It is SMALLER though  The involved string operations are slim in high level language code  SQL and PHP   but expensive compared to using arrays of integers  Databases are not meant to be human readable  and it is mostly stupid to try to stick to structures due to their readability   direct editability  as I did    In short  there is a reason why there is no native SPLIT   function in MySQL

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You can create a function for this         Split a string by string  Similar to the php function explode         param VARCHAR 12  delim The boundary string  delimiter      param VARCHAR 255  str The input string     param INT pos The index of the string to return    return VARCHAR 255  The  pos th substring    return VARCHAR 255  Returns the  pos th string created by splitting the str parameter on boundaries formed by the delimiter       example       SELECT SPLIT STRING       one two three four   1         This query        DROP FUNCTION IF EXISTS SPLIT STRING  CREATE FUNCTION SPLIT STRING delim VARCHAR 12   str VARCHAR 255   pos INT  RETURNS VARCHAR 255  DETERMINISTIC RETURN     REPLACE          SUBSTRING              SUBSTRING INDEX str  delim  pos               LENGTH SUBSTRING INDEX str  delim  pos-1     1                    delim              Converting the magical pseudocode to use this  you would have   SELECT e  studentId   SPLIT STRING      c  courseNames   e  courseId   FROM

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Here s what I ve got so far  found it on the page Ben Alpert mentioned    SELECT REPLACE      SUBSTRING          SUBSTRING INDEX c  courseNames        e  courseId    1            LENGTH SUBSTRING INDEX c  courseNames        e  courseId           1                       FROM  clients  c INNER JOIN  clientenrols  e USING   clientId

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I just had a similar issue with a field like that which I solved a different way  My use case was needing to take those ids in a comma separated list for use in a join   I was able to solve it using a like  but it was made easier because in addition to the comma delimiter the ids were also quoted like so    keys  1   2   6   12    Because of that  I was able to do a LIKE   SELECT twwf id  jtwi id joined id FROM table with weird field twwf   INNER JOIN join table with ids jtwi      ON twwf delimited field LIKE CONCAT        jtwi id           This basically just looks to see if the id from the table you re trying to join appears in the set and at that point you can join on it easily enough and return your records  You could also just create a view from something like this   It worked well for my use case where I was dealing with a Wordpress plugin that managed relations in the way described  The quotes really help though because otherwise you run the risk of partial matches  aka - id 1 within 18  etc

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I used the above logic but modified it slightly   My input is of format    apple 100 pinapple 200 orange 300  stored in a variable  updtAdvanceKeyVal  Here is the function block    set  res        set  i   1  set  updtAdvanceKeyVal   updtAdvanceKeyVal   REPEAT    -- set r    replace SUBSTRING SUBSTRING INDEX  updtAdvanceKeyVal        i    --  LENGTH SUBSTRING INDEX  updtAdvanceKeyVal        i -1     1            -- wrapping the function in  replace  function as above causes to cut off a character from  -- the 2nd splitted value if the value is more than 3 characters  Writing it in 2 lines causes no such problem and the output is as expected -- sample output by executing the above function   -- orange 100 -- pi apple 200            strange output         -- tomato 500        set  r    SUBSTRING SUBSTRING INDEX  updtAdvanceKeyVal        i                     LENGTH SUBSTRING INDEX  updtAdvanceKeyVal        i -1     1          set  r   replace  r                 if  r  lt  gt     then                set  key   SUBSTRING INDEX  r      1                 set  val   SUBSTRING INDEX  r      -1                  select  key   val        end if         set  i    i   1        until  r      END REPEAT

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Here s how you do it for SQL Server  Someone else can translate it to MySQL  Parsing CSV Values Into Multiple Rows   SELECT Author   NullIf SubString       Phrase         ID   CharIndex             Phrase         ID  - ID        AS Word  FROM Tally  Quotes  WHERE ID  lt   Len       Phrase        AND SubString       Phrase         ID - 1  1         AND CharIndex             Phrase         ID  - ID  gt  0   The idea is to cross join to a predefined table Tally which contains integer 1 through 8000  or whatever big enough number  and run SubString to find the right  word  position

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There s an easier way  have a link table  i e    Table 1  clients  client info  blah blah blah  Table 2  courses  course info  blah blah  Table 3  clientid  courseid  Then do a JOIN and you re off to the races

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SELECT   tab1 std name  tab1 stdCode  tab1 payment    SUBSTRING INDEX tab1 payment       1  as rupees    SUBSTRING tab1 payment  LENGTH SUBSTRING INDEX tab1 payment       1     2 LENGTH SUBSTRING INDEX tab1 payment       2    as date FROM     SELECT DISTINCT     si std name  hfc stdCode      if isnull hfc payDate   concat hfc coutionMoneyIn      year hfc startDtae    -    monthname hfc startDtae    concat hfc payMoney       monthname hfc payDate    -   year hfc payDate    AS payment   FROM hostelfeescollection hfc   INNER JOIN hostelfeecollectmode hfm ON hfc tranId   hfm tranId   INNER JOIN student info 1 si ON si std code   hfc stdCode   WHERE hfc tranId    TRAN-AZZZY69454    AS tab1

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MySQL s only string-splitting function is SUBSTRING INDEX str  delim  count   You can use this  to  for example    Return the item before the first separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        1    --------------------------------------------    SUBSTRING INDEX  foo bar baz qux        1     --------------------------------------------    foo                                           --------------------------------------------  1 row in set  0 00 sec   Return the item after the last separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        -1    ---------------------------------------------    SUBSTRING INDEX  foo bar baz qux        -1     ---------------------------------------------    qux                                            ---------------------------------------------  1 row in set  0 00 sec   Return everything before the third separator in a string   mysql gt  SELECT SUBSTRING INDEX  foo bar baz qux        3    --------------------------------------------    SUBSTRING INDEX  foo bar baz qux        3     --------------------------------------------    foo bar baz                                   --------------------------------------------  1 row in set  0 00 sec   Return the second item in a string  by chaining two calls   mysql gt  SELECT SUBSTRING INDEX SUBSTRING INDEX  foo bar baz qux        2        -1    ----------------------------------------------------------------------    SUBSTRING INDEX SUBSTRING INDEX  foo bar baz qux        2        -1     ----------------------------------------------------------------------    bar                                                                     ----------------------------------------------------------------------  1 row in set  0 00 sec     In general  a simple way to get the nth element of a  -separated string  assuming that you know it definitely has at least n elements  is to do   SUBSTRING INDEX SUBSTRING INDEX your string       n        -1     The inner SUBSTRING INDEX call discards the nth separator and everything after it  and then the outer SUBSTRING INDEX call discards everything except the final element that remains   If you want a more robust solution that returns NULL if you ask for an element that doesn t exist  for instance  asking for the 5th element of  a b c d    then you can count the delimiters using REPLACE and then conditionally return NULL using IF     IF      LENGTH your string  - LENGTH REPLACE your string              LENGTH       lt  n - 1      NULL      SUBSTRING INDEX SUBSTRING INDEX your string       n        -1      Of course  this is pretty ugly and hard to understand  So you might want to wrap it in a function   CREATE FUNCTION split string TEXT  delimiter TEXT  n INT  RETURNS TEXT DETERMINISTIC RETURN IF       LENGTH string  - LENGTH REPLACE string  delimiter          LENGTH delimiter   lt  n - 1      NULL      SUBSTRING INDEX SUBSTRING INDEX string  delimiter  n   delimiter  -1       You can then use the function like this   mysql gt  SELECT SPLIT  foo bar baz qux        3    ----------------------------------    SPLIT  foo bar baz qux        3     ----------------------------------    baz                                 ----------------------------------  1 row in set  0 00 sec   mysql gt  SELECT SPLIT  foo bar baz qux        5    ----------------------------------    SPLIT  foo bar baz qux        5     ----------------------------------    NULL                                ----------------------------------  1 row in set  0 00 sec   mysql gt  SELECT SPLIT  foo   bar   baz   qux          2    ------------------------------------------    SPLIT  foo   bar   baz   qux          2     ------------------------------------------    bar                                         ------------------------------------------  1 row in set  0 00 sec

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Based on Alex answer above  https   stackoverflow com a 11022431 1466341  I came up with even better solution  Solution which doesn t contain exact one record ID   Assuming that the comma separated list is in table data list  and it contains listing of codes from other table classification code  you can do something like   SELECT      d id  d list  c code FROM      classification c     JOIN data d         ON d list REGEXP CONCAT      lt       c code       gt          So if you have tables and data like this   CLASSIFICATION  code varchar 4  unique     A      B      C      D   MY DATA  id int  list varchar 255     100   C A B     150   B A D     200  B     above SELECT will return   100   C A B    A     100   C A B    B     100   C A B    C     150   B A D    A     150   B A D    B     150   B A D    D     200   B    B

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There s an easier way  have a link table  i e    Table 1  clients  client info  blah blah blah  Table 2  courses  course info  blah blah  Table 3  clientid  courseid  Then do a JOIN and you re off to the races

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There s an easier way  have a link table  i e    Table 1  clients  client info  blah blah blah  Table 2  courses  course info  blah blah  Table 3  clientid  courseid  Then do a JOIN and you re off to the races

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I ve resolved this kind of problem with a regular expression pattern  They tend to be slower than regular queries but it s an easy way to retrieve data in a comma-delimited query column  SELECT    FROM  TABLE  WHERE  field  REGEXP     SEARCHED-VALUE        the greedy question mark helps to search at the beggining or the end of the string   Hope that helps for anyone in the future

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Here s what I ve got so far  found it on the page Ben Alpert mentioned    SELECT REPLACE      SUBSTRING          SUBSTRING INDEX c  courseNames        e  courseId    1            LENGTH SUBSTRING INDEX c  courseNames        e  courseId           1                       FROM  clients  c INNER JOIN  clientenrols  e USING   clientId

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You can do this with JSON in more recent MySQL versions  It s a blast  We will have a quick preparation to create a numbers table  Then first we create an intermediary table to convert the comma delimited strings into a json array then we will use json extract to blast them apart  I am encapsulating the strings in quotes carefully escaping existing quotes because I had semicolon separated strings containing commas    So to create the numbers table  hopefully you have more clients than courses  choose an adequately big table if not   CREATE TABLE numbers  n int PRIMARY KEY   INSERT INTO numbers  SELECT  row     row   1 FROM clients JOIN  select  row  0  t2    Add LIMIT 50 if you know you only have 50 courses  Now  that was easy  wasn t it  Now on to the real work  honestly it s the quotes that make it uglier but at least it s more generic that way   CREATE TABLE json coursenames  SELECT clientId clientName CONCAT       REPLACE REPLACE courseName                                AS a FROM clients   CREATE TABLE extracted SELECT clientId clientName REPLACE TRIM TRIM     FROM JSON EXTRACT a  concat       n                       FROM json coursenames INNER JOIN numbers ON n  lt  JSON LENGTH a     Wheee   The meat here are these two  the CONCAT       REPLACE coursename                      I dropped the second REPLACE to make it more visible  will convert foo bar bar into  foo   bar   baz   The other trick is JSON EXTRACT a  concat       n       will become JSON EXTRACT a    12   and that s the 13th element in the array  see JSON Path syntax

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I just had a similar issue with a field like that which I solved a different way  My use case was needing to take those ids in a comma separated list for use in a join   I was able to solve it using a like  but it was made easier because in addition to the comma delimiter the ids were also quoted like so    keys  1   2   6   12    Because of that  I was able to do a LIKE   SELECT twwf id  jtwi id joined id FROM table with weird field twwf   INNER JOIN join table with ids jtwi      ON twwf delimited field LIKE CONCAT        jtwi id           This basically just looks to see if the id from the table you re trying to join appears in the set and at that point you can join on it easily enough and return your records  You could also just create a view from something like this   It worked well for my use case where I was dealing with a Wordpress plugin that managed relations in the way described  The quotes really help though because otherwise you run the risk of partial matches  aka - id 1 within 18  etc

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Well  nothing I used worked  so I decided creating a real simple split function  hope it helps       DECLARE inipos INTEGER      DECLARE endpos INTEGER      DECLARE maxlen INTEGER      DECLARE item VARCHAR 100       DECLARE delim VARCHAR 1        SET delim            SET inipos   1      SET fullstr   CONCAT fullstr  delim       SET maxlen   LENGTH fullstr        REPEAT         SET endpos   LOCATE delim  fullstr  inipos           SET item    SUBSTR fullstr  inipos  endpos - inipos            IF item  lt  gt     AND item IS NOT NULL THEN                        USE THE ITEM STRING          END IF          SET inipos   endpos   1      UNTIL inipos  gt   maxlen END REPEAT

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Well  nothing I used worked  so I decided creating a real simple split function  hope it helps       DECLARE inipos INTEGER      DECLARE endpos INTEGER      DECLARE maxlen INTEGER      DECLARE item VARCHAR 100       DECLARE delim VARCHAR 1        SET delim            SET inipos   1      SET fullstr   CONCAT fullstr  delim       SET maxlen   LENGTH fullstr        REPEAT         SET endpos   LOCATE delim  fullstr  inipos           SET item    SUBSTR fullstr  inipos  endpos - inipos            IF item  lt  gt     AND item IS NOT NULL THEN                        USE THE ITEM STRING          END IF          SET inipos   endpos   1      UNTIL inipos  gt   maxlen END REPEAT

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Based on Alex answer above  https   stackoverflow com a 11022431 1466341  I came up with even better solution  Solution which doesn t contain exact one record ID   Assuming that the comma separated list is in table data list  and it contains listing of codes from other table classification code  you can do something like   SELECT      d id  d list  c code FROM      classification c     JOIN data d         ON d list REGEXP CONCAT      lt       c code       gt          So if you have tables and data like this   CLASSIFICATION  code varchar 4  unique     A      B      C      D   MY DATA  id int  list varchar 255     100   C A B     150   B A D     200  B     above SELECT will return   100   C A B    A     100   C A B    B     100   C A B    C     150   B A D    A     150   B A D    B     150   B A D    D     200   B    B

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Seeing that it s a fairly popular question - the answer is YES   For a column column in table table containing all of your coma separated values   CREATE TEMPORARY TABLE temp  val CHAR 255    SET  S1   CONCAT  INSERT INTO temp  val  VALUES     REPLACE  SELECT GROUP CONCAT  DISTINCT   column   AS data FROM  table                          PREPARE stmt1 FROM  s1  EXECUTE stmt1  SELECT DISTINCT val  FROM temp      Please remember however to not store CSV in your DB    Per  Mark Amery - as this translates coma separated values into an INSERT statement  be careful when running it on unsanitised data    Just to reiterate  please don t store CSV in your DB  this function is meant to translate CSV into sensible DB structure and not to be used anywhere in your code  If you have to use it in production  please rethink your DB structure

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Here s what I ve got so far  found it on the page Ben Alpert mentioned    SELECT REPLACE      SUBSTRING          SUBSTRING INDEX c  courseNames        e  courseId    1            LENGTH SUBSTRING INDEX c  courseNames        e  courseId           1                       FROM  clients  c INNER JOIN  clientenrols  e USING   clientId

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Here s how you do it for SQL Server  Someone else can translate it to MySQL  Parsing CSV Values Into Multiple Rows   SELECT Author   NullIf SubString       Phrase         ID   CharIndex             Phrase         ID  - ID        AS Word  FROM Tally  Quotes  WHERE ID  lt   Len       Phrase        AND SubString       Phrase         ID - 1  1         AND CharIndex             Phrase         ID  - ID  gt  0   The idea is to cross join to a predefined table Tally which contains integer 1 through 8000  or whatever big enough number  and run SubString to find the right  word  position

[mysql] Can you split/explode a field in a MySQL query?

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