mysql> show engines;
+------------+---------+---------------------------------------------------
-------------+
| Engine | Support | Comment
|
+------------+---------+---------------------------------------------------
-------------+
| MyISAM | YES | Default engine as of MySQL 3.23 with great perform
ance |
| MEMORY | YES | Hash based, stored in memory, useful for temporary
tables |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and fore
ign keys |
| BerkeleyDB | NO | Supports transactions and page-level locking
|
| BLACKHOLE | NO | /dev/null storage engine (anything you write to it
disappears) |
| EXAMPLE | NO | Example storage engine
|
| ARCHIVE | YES | Archive storage engine
|
| CSV | NO | CSV storage engine
|
| ndbcluster | NO | Clustered, fault-tolerant, memory-based tables
|
| FEDERATED | NO | Federated MySQL storage engine
|
| MRG_MYISAM | YES | Collection of identical MyISAM tables
|
| ISAM | NO | Obsolete storage engine
|
+------------+---------+---------------------------------------------------
-------------+
12 rows in set (0.00 sec)
 

mysql> create database tests;
Query OK, 1 row affected (0.02 sec)
 

mysql> create table users
-> (
-> UserID int(4) auto_increment primary key,
-> UserName varchar(81),
-> age int(3),
-> CONSTRAINT chk_age CHECK(age >=18 )
-> )ENGINE=INNODB;
Query OK, 0 rows affected (0.11 sec)


 

mysql> insert into users
-> value (1,'mrxau',15);
Query OK, 1 row affected (0.05 sec)

mysql> insert into users
-> value (0,'mrxau',19);
Query OK, 1 row affected (0.03 sec)

 

mysql> select * from users;
+--------+----------+------+
| UserID | UserName | age |
+--------+----------+------+
| 1 | mrxau | 15 |
| 2 | mrxau | 19 |
+--------+----------+------+
2 rows in set (0.00 sec)
 

The CHECK clause is parsed but [BIG]ignored[/BIG] by all storage engines.