MySQL query to convert empty values to NULL?

It’s easy to convert empty values to NULL using SET and WHERE. Let us first create a table −

mysql> create table DemoTable1315 -> ( -> CountryName varchar(10) -> ); Query OK, 0 rows affected (0.60 sec)

Insert some records in the table using insert command. We have set some empty values here as well −

mysql> insert into DemoTable1315 values('US'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1315 values(''); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable1315 values('UK'); Query OK, 1 row affected (0.70 sec) mysql> insert into DemoTable1315 values(''); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1315 values(''); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1315 values('AUS'); Query OK, 1 row affected (0.14 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable1315;

Output

+-------------+ | CountryName | +-------------+ | US          | |             | | UK          | |             | |             | | AUS         | +-------------+ 6 rows in set (0.00 sec)

Here is the query to convert empty values to NULL −

mysql> update DemoTable1315 set CountryName=NULL where CountryName=''; Query OK, 3 rows affected (0.16 sec) Rows matched: 3 Changed: 3 Warnings: 0

Let us check the table records once again −

mysql> select *from DemoTable1315;

Output

+-------------+ | CountryName | +-------------+ | US          | | NULL        | | UK          | | NULL        | | NULL | | AUS | +-------------+ 6 rows in set (0.00 sec)