Implement MySQL CASE statement with WHEN clause

CASE statement with the WHEN clause is used to work around conditions. Following is the syntax−

select *,
   case when yourCondition then yourStatement
   when yourCondition then yourStatement
   .
   .
else yourStatement
from yourTableName;

Let us first create a table −

mysql> create table DemoTable
   -> (
   -> StudentName varchar(20),
   -> StudentMarks int
   -> );
Query OK, 0 rows affected (0.77 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('Chris',78);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values('Robert',88);
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('Mike',75);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values('Sam',98);
Query OK, 1 row affected (0.16 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+-------------+--------------+
| StudentName | StudentMarks |
+-------------+--------------+
| Chris       |           78 |
| Robert      |           88 |
| Mike        |           75 |
| Sam         |           98 |
+-------------+--------------+
4 rows in set (0.00 sec)

Here is the query to implement MySQL CASE WHEN −

mysql> select *,
   -> case when StudentMarks > 90 then 'Very Good Score'
   -> when StudentMarks > 80 then 'Good Score'
   -> else
   -> 'Not Good'
   -> end as Status
   -> from DemoTable;

This will produce the following output −

+-------------+--------------+-----------------+
| StudentName | StudentMarks |    Status       |
+-------------+--------------+-----------------+
| Chris       |           78 | Not Good        |
| Robert      |           88 | Good Score      |
| Mike        |           75 | Not Good        |
| Sam         |           98 | Very Good Score |
+-------------+--------------+-----------------+
4 rows in set (0.00 sec)