How to update column with null value

Question

I am using mysql and need to update a column with a null value  I have tried this many different ways and the best I have gotten is an empty string   Is there a special syntax to do this

User · Answer

I suspect the problem here is that quotes were entered as literals in your string value. You can set these columns to null using:

UPDATE table SET col=NULL WHERE length(col)<3;

You should of course first check that these values are indeed "" with something like:

SELECT DISTINCT(col) FROM table WHERE length(col)<3;

User · Answer

NULL is a special value in SQL  So to null a property  do this   UPDATE table SET column   NULL

User · Answer

Use IS instead of   This will solve your problem  example syntax    UPDATE studentdetails SET contactnumber   9098979690 WHERE contactnumber IS NULL

User · Answer

if you set NULL for all records try this   UPDATE  table name  SET  column you want set null   NULL   OR just set NULL for special records use WHERE   UPDATE  table name  SET  column you want set null   NULL WHERE  column name     column value

User · Answer

On insert we can use  arrEntity  entity- gt toArray                foreach   arrEntity as  key   gt   value                if  trim  entity- gt  key         amp  amp   is null  entity- gt  key   amp  amp   is bool  entity- gt  key            unset  entity- gt  key                    On update we can use  fields array    foreach   fields as  key   gt   value            if  trim  value         amp  amp   is null  value   amp  amp   is bool  value                 fields  key    null

User · Answer

Remember to look if your column can be null  You can do that using  mysql gt  desc my table    If your column cannot be null  when you set the value to null it will be the cast value to it   Here a example  mysql gt  create table example   age int not null  name varchar 100  not null    mysql gt  insert into example values   null   without num       2   null    mysql gt  select   from example   ----- -------------    age   name           ----- -------------      0   without num       2                  ----- -------------  2 rows in set  0 00 sec   mysql gt  select   from example where age is null or name is null  Empty set  0 00 sec

User · Answer

For those facing a similar issue  I found that when  simulating  a SET   NULL query  PHPMyAdmin would throw an error  It s a red herring   just run the query and all will be well

User · Answer

use is instead of    Eg  Select   from table name where column is null

User · Answer

if you follow   UPDATE table SET name   NULL   then name is    not NULL IN MYSQL means your query   SELECT   FROM table WHERE name   NULL  not work or disappoint yourself

User · Answer

In the above answers  many ways and repetitions have been suggested for the same  I kept looking for an answer as mentioned is the question but couldn t find here  Another way to put the above question  quot update a column with a null value quot  could be  quot UPDATE ALL THE ROWS IN THE COLUMN TO NULL quot  In such a situation following works update table name set field name   NULL where field name is not NULL   is as well is not works in mysql

User · Answer

No special syntax   CREATE TABLE your table  some id int  your column varchar 100     INSERT INTO your table VALUES  1   Hello     UPDATE your table SET    your column   NULL WHERE  some id   1   SELECT   FROM your table WHERE your column IS NULL   --------- -------------    some id   your column    --------- -------------          1   NULL           --------- -------------  1 row in set  0 00 sec

User · Answer

If you want to set null value using update query set column value to NULL  without quotes  update tablename set columnname   NULL   However  if you are directly editing field value inside mysql workbench then use  Esc   del  keystroke to insert null value into selected column

User · Answer

Another possible reason for the empty string  rather than a true null is that the field is an index or is part of an index   This happened to me  using phpMyAdmin  I edited the structure of a field in one of my tables to allow NULLs by checking the  Null  checkbox then hitting the  Save  button    Table pricing has been altered successfully  was displayed so I assumed that the change happened -- it didn t   After doing an UPDATE to set all of those fields to NULL  they were  instead  set to empty strings  so I took a look at the table structure again and saw that the  Null  column for that field was set to  no    That s when I realized that the field was part of the Primary key

[mysql] How to update column with null value

Examples related to mysql

Examples related to sql-update