Can we use WHERE clause inside MySQL CASE statement?

For this, use the CASE WHEN statement. Let us first create a table −

mysql> create table DemoTable1040 (    Value1 int,    Value2 int,    Value3 int ); Query OK, 0 rows affected (0.65 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1040 values(10,30,1); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1040 values(40,20,50); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1040 values(80,90,100); Query OK, 1 row affected (0.11 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable1040;

This will produce the following output −

+--------+--------+--------+ | Value1 | Value2 | Value3 | +--------+--------+--------+ |     10 |     30 |      1 | |     40 |     20 |     50 | |     80 |     90 |    100 | +--------+--------+--------+ 3 rows in set (0.00 sec)

Following is the query to use CASE WHEN −

mysql> select case when (Value1=40 AND Value2=20) then Value2 else Value1 end as selectedValue from DemoTable1040;

This will produce the following output −

+---------------+ | selectedValue | +---------------+ |            10 | | 20 | | 80 | +---------------+ 3 rows in set (0.00 sec)