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Expression in CASE WHEN Clause doesn't work in MySQL query?
Fir this, use CASE WHEN statement in MySQL correctly. Let us see how.
Let us create a table −
mysql> create table demo58 −> ( −> id int not null auto_increment primary key, −> first_name varchar(20), −> last_name varchar(20) −> ); Query OK, 0 rows affected (2.15 sec)
Insert some records into the table with the help of insert command −
mysql> insert into demo58(first_name,last_name) values('John','Doe');
Query OK, 1 row affected (0.12 sec)
mysql> insert into demo58(first_name,last_name) values('David','Smith');
Query OK, 1 row affected (0.29 sec)
mysql> insert into demo58(first_name,last_name) values('John','Brown');
Query OK, 1 row affected (0.11 sec)
mysql> insert into demo58(first_name,last_name) values('David','Miller');
Query OK, 1 row affected (0.26 sec)Display records from the table using select statement −
mysql> select *from demo58;
This will produce the following output −
+----+------------+-----------+ | id | first_name | last_name | +----+------------+-----------+ | 1 | John | Doe | | 2 | David | Smith | | 3 | John | Brown | | 4 | David | Miller | +----+------------+-----------+ 4 rows in set (0.15 sec)
Following is the query for expression in CASE WHEN −
mysql> select −> ( −> case −> when (first_name = "John") then 'Carol' −> when (last_name ="Smith") then 'Doe' −> end −> ) RESULT −> from demo58;
This will produce the following output −
+--------+ | RESULT | +--------+ | Carol | | Doe | | Carol | | NULL | +--------+ 4 rows in set (0.00 sec)
Updated on: 20-Nov-2020
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