How to replace rows in a MySQL table with conditions?

To set conditions and replace rows, use MySQL CASE statement. Let us first create a table −

mysql> create table DemoTable1481
   -> (
   -> PlayerScore int
   -> );
Query OK, 0 rows affected (0.42 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1481 values(454);
Query OK, 1 row affected (0.41 sec)
mysql> insert into DemoTable1481 values(765);
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable1481 values(890);
Query OK, 1 row affected (0.09 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1481;

This will produce the following output −

+-------------+
| PlayerScore |
+-------------+
|         454 |
|         765 |
|         890 |
+-------------+
3 rows in set (0.00 sec)

Following is the query to replace rows in a MySQL table −

mysql> update DemoTable1481
   -> set PlayerScore= case when PlayerScore=454 then 1256
   -> when PlayerScore=765 then 1865
   -> when PlayerScore=890 then 3990
   -> end
   -> ;
Query OK, 3 rows affected (0.17 sec)
Rows matched: 3  Changed: 3 Warnings: 0

Let us check the table records once again −

mysql> select * from DemoTable1481;

This will produce the following output −

+-------------+
| PlayerScore |
+-------------+
|        1256 |
|        1865 |
|        3990 |
+-------------+
3 rows in set (0.00 sec)