MySQL update column to NULL for blank values

For this, you can use IF() along with UPDATE command. Let us first create a table −

mysql> create table DemoTable1601    -> (    -> FirstName varchar(20) ,    -> LastName varchar(20)    -> ); Query OK, 0 rows affected (0.53 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1601 values('John','Doe'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1601 values('Adam',''); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1601 values('David','Miller'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1601 values('Chris',''); Query OK, 1 row affected (0.11 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1601;

This will produce the following output −

+-----------+----------+ | FirstName | LastName | +-----------+----------+ | John      |      Doe | | Adam      |          | | David     |   Miller | | Chris     |          | +-----------+----------+ 4 rows in set (0.00 sec)

Following is the query to update column to null or its value −

mysql> update DemoTable1601 set LastName=if(LastName='',NULL,LastName); Query OK, 2 rows affected (0.22 sec) Rows matched: 4  Changed: 2 Warnings: 0

Let us check the table records once again −

mysql> select * from DemoTable1601;

This will produce the following output −

+-----------+----------+ | FirstName | LastName | +-----------+----------+ | John      |      Doe | | Adam      |     NULL | | David     |   Miller | | Chris     |     NULL | +-----------+----------+ 4 rows in set (0.00 sec)