Syntax error MySQL update column to NULL for blank values

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)
Updated on: 2019-12-16T07:35:34+05:30

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