Set different IDs for records with conditions using a single MySQL query

For conditions, use CASE statement in MySQL. Let us first create a table −

mysql> create table DemoTable1545    -> (    -> Id int,    -> FirstName varchar(20)    -> ); Query OK, 0 rows affected (1.65 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1545 values(1,'John'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1545 values(2,'Chris'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1545 values(3,'Bob'); Query OK, 1 row affected (0.15 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1545;

This will produce the following output −

+------+-----------+ | Id   | FirstName | +------+-----------+ |    1 | John      | |    2 | Chris     | |    3 | Bob       | +------+-----------+ 3 rows in set (0.00 sec)

Here is the query to set different IDs using CASE statement −

mysql> update DemoTable1545    -> set Id=    -> case when FirstName like '%John%' then 101    -> when FirstName like '%Chris%' then 201    -> when FirstName like '%Bob%' then 501    -> else Id    -> end; Query OK, 3 rows affected (0.18 sec) Rows matched: 3  Changed: 3 Warnings: 0

Let us check the table records once again −

mysql> select * from DemoTable1545;

This will produce the following output −

+------+-----------+ | Id   | FirstName | +------+-----------+ |  101 | John      | |  201 | Chris     | |  501 | Bob       | +------+-----------+ 3 rows in set (0.00 sec)