How to declare a variable in MySQL

Question

How to declare a variable in mysql  so that my second query can use it   I would like to write something like   SET start   1  SET finish   10   SELECT   FROM places WHERE place BETWEEN start AND finish

User · Answer

Use set or select  SET  counter    100  SELECT  variable name    value      example     SELECT  price    MAX product price  FROM product

User · Answer

Declare  SET  a   1  Usage  INSERT INTO  t    c   VALUES   a

User · Answer

There are mainly three types of variables in MySQL    User-defined variables  prefixed with        You can access any user-defined variable without declaring it or initializing it  If you refer to a variable that has not been initialized  it has a value of NULL and a type of string   SELECT  var any var name   You can initialize a variable using SET or SELECT statement   SET  start   1   finish   10        or   SELECT  start    1   finish    10   SELECT   FROM places WHERE place BETWEEN  start AND  finish    User variables can be assigned a value from a limited set of data types  integer  decimal  floating-point  binary or nonbinary string  or NULL value   User-defined variables are session-specific  That is  a user variable defined by one client cannot be seen or used by other clients   They can be used in SELECT queries using Advanced MySQL user variable techniques  Local Variables  no prefix     Local variables needs to be declared using DECLARE before accessing it   They can be used as local variables and the input parameters inside a stored procedure      DELIMITER     CREATE PROCEDURE sp test var1 INT   BEGIN        DECLARE start  INT unsigned DEFAULT 1        DECLARE finish INT unsigned DEFAULT 10       SELECT  var1  start  finish       SELECT   FROM places WHERE place BETWEEN start AND finish   END      DELIMITER    CALL sp test 5     If the DEFAULT clause is missing  the initial value is NULL    The scope of a local variable is the BEGIN     END block within which it is declared  Server System Variables  prefixed with       The MySQL server maintains many system variables configured to a default value  They can be of type GLOBAL  SESSION or BOTH   Global variables affect the overall operation of the server whereas session variables affect its operation for individual client connections   To see the current values used by a running server  use the SHOW VARIABLES statement or SELECT   var name    SHOW VARIABLES LIKE   wait timeout     SELECT   sort buffer size    They can be set at server startup using options on the command line or in an option file   Most of them can be changed dynamically while the server is running using SET GLOBAL or SET SESSION   -- Syntax to Set value to a Global variable  SET GLOBAL sort buffer size 1000000  SET   global sort buffer size 1000000   -- Syntax to Set value to a Session variable  SET sort buffer size 1000000  SET SESSION sort buffer size 1000000  SET   sort buffer size 1000000  SET   local sort buffer size 10000

User · Answer

SET Value   declare Regione int      set Regione  select  id from users  where id 1     select Regione

User · Answer

Different types of variable    local variables  which are not prefixed by    are strongly typed and scoped to the stored program block in which they are declared  Note that  as documented under DECLARE Syntax    DECLARE is permitted only inside a BEGIN     END compound statement and must be at its start  before any other statements    User variables  which are prefixed by    are loosely typed and scoped to the session  Note that they neither need nor can be declared   just use them directly    Therefore  if you are defining a stored program and actually do want a  local variable   you will need to drop the   character and ensure that your DECLARE statement is at the start of your program block  Otherwise  to use a  user variable   drop the DECLARE statement   Furthermore  you will either need to surround your query in parentheses in order to execute it as a subquery      SET  countTotal    SELECT COUNT    FROM nGrams     Or else  you could use SELECT     INTO      SELECT COUNT    INTO  countTotal FROM nGrams

User · Answer

For any person using  variable in concat ws function to get concatenated values  don t forget to reinitialize it with empty value  Otherwise it can use old value for same session   Set  Ids        select     Ids    concat ws      Ids tbl Id     tbl Col1        from mytable tbl

User · Answer

SET   SET  var name   value    OR   SET  var    value   both operators   and    are accepted       SELECT   SELECT col1   var name    col2 from tb name WHERE  conditon     if multiple record sets found only the last value in col2 is keep  override    SELECT col1  col2 INTO  var name  col3 FROM         in this case the result of select is not containing col2 values    Ex both methods used   -- TRIGGER BEFORE INSERT --- setting a column value from calculations      SELECT count    INTO  NR FROM a table WHERE a condition  SET NEW ord col    IFNULL   NR  0     1

[mysql] How to declare a variable in MySQL?

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