MySQL replacement field in the Data Content section string

MySQL replaces the contents of the table field, as in the example:

Mysql> Select Host,user from user where user= ' testuser ';
+-----------------------+----------+
| Host | user |
+-----------------------+----------+
| Localhost.localdomain| TestUser |
+-----------------------+----------+

Update the contents of the host, change "main" to "slave" and replace

mysql> Update user set Host=replace (host, ' main ', ' slave ') where user= ' testuser ';
Query OK, 1 row Affected (0.00 sec)
Rows matched:1 changed:1 warnings:0

Mysql> Select Host,user from user where user= ' testuser ';
+------------------------+----------+
| Host | user |
+------------------------+----------+
| Localhost.localdoslave | testuser |
+------------------------+----------+

The data has been updated successfully by the result of the query

MySQL replacement field in the Data Content section string