tidb: add description about TIDB_CHECK_CONSTRAINTS (#18753)

TOC-tidb-cloud.md

@@ -655,6 +655,7 @@
         - [`TABLES`](/information-schema/information-schema-tables.md)
         - [`TABLE_CONSTRAINTS`](/information-schema/information-schema-table-constraints.md)
         - [`TABLE_STORAGE_STATS`](/information-schema/information-schema-table-storage-stats.md)
+        - [`TIDB_CHECK_CONSTRAINTS`](/information-schema/information-schema-tidb-check-constraints.md)
         - [`TIDB_HOT_REGIONS_HISTORY`](/information-schema/information-schema-tidb-hot-regions-history.md)
         - [`TIDB_INDEXES`](/information-schema/information-schema-tidb-indexes.md)
         - [`TIDB_INDEX_USAGE`](/information-schema/information-schema-tidb-index-usage.md)

TOC.md

@@ -994,6 +994,7 @@
         - [`TABLES`](/information-schema/information-schema-tables.md)
         - [`TABLE_CONSTRAINTS`](/information-schema/information-schema-table-constraints.md)
         - [`TABLE_STORAGE_STATS`](/information-schema/information-schema-table-storage-stats.md)
+        - [`TIDB_CHECK_CONSTRAINTS`](/information-schema/information-schema-tidb-check-constraints.md)
         - [`TIDB_HOT_REGIONS`](/information-schema/information-schema-tidb-hot-regions.md)
         - [`TIDB_HOT_REGIONS_HISTORY`](/information-schema/information-schema-tidb-hot-regions-history.md)
         - [`TIDB_INDEXES`](/information-schema/information-schema-tidb-indexes.md)

information-schema/information-schema-check-constraints.md

@@ -29,6 +29,7 @@ The output is as follows:
 The following example adds a `CHECK` constraint using the `CREATE TABLE` statement:
 
 ```sql
+SET GLOBAL tidb_enable_check_constraint = ON;
 CREATE TABLE test.t1 (id INT PRIMARY KEY, CHECK (id%2 = 0));
 SELECT * FROM CHECK_CONSTRAINTS\G
 ```

information-schema/information-schema-tidb-check-constraints.md

@@ -0,0 +1,59 @@
+---
+title: TIDB_CHECK_CONSTRAINTS
+summary: Learn the `TIDB_CHECK_CONSTRAINTS` INFORMATION_SCHEMA table.
+---
+
+# TIDB\_CHECK\_CONSTRAINTS
+
+The `TIDB_CHECK_CONSTRAINTS` table provides information about [`CHECK` constraints](/constraints.md#check) on tables. In addition to the columns in [`CHECK_CONSTRAINTS`](/information-schema/information-schema-check-constraints.md), `TIDB_CHECK_CONSTRAINTS` provides the name and ID of the table that defines the `CHECK` constraint.
+
+```sql
+USE INFORMATION_SCHEMA;
+DESC TIDB_CHECK_CONSTRAINTS;
+```
+
+The output is as follows:
+
+```sql
++--------------------+-------------+------+------+---------+-------+
+| Field              | Type        | Null | Key  | Default | Extra |
++--------------------+-------------+------+------+---------+-------+
+| CONSTRAINT_CATALOG | varchar(64) | NO   |      | NULL    |       |
+| CONSTRAINT_SCHEMA  | varchar(64) | NO   |      | NULL    |       |
+| CONSTRAINT_NAME    | varchar(64) | NO   |      | NULL    |       |
+| CHECK_CLAUSE       | longtext    | NO   |      | NULL    |       |
+| TABLE_NAME         | varchar(64) | YES  |      | NULL    |       |
+| TABLE_ID           | bigint(21)  | YES  |      | NULL    |       |
++--------------------+-------------+------+------+---------+-------+
+6 rows in set (0.00 sec)
+```
+
+The following example adds a `CHECK` constraint using the `CREATE TABLE` statement:
+
+```sql
+SET GLOBAL tidb_enable_check_constraint = ON;
+CREATE TABLE test.t1 (id INT PRIMARY KEY, CHECK (id%2 = 0));
+SELECT * FROM TIDB_CHECK_CONSTRAINTS\G
+```
+
+The output is as follows:
+
+```sql
+*************************** 1. row ***************************
+CONSTRAINT_CATALOG: def
+ CONSTRAINT_SCHEMA: test
+   CONSTRAINT_NAME: t1_chk_1
+      CHECK_CLAUSE: (`id` % 2 = 0)
+        TABLE_NAME: t1
+          TABLE_ID: 107
+1 row in set (0.02 sec)
+```
+
+Fields in the `TIDB_CHECK_CONSTRAINTS` table are described as follows:
+
+* `CONSTRAINT_CATALOG`: The catalog of the constraint, which is always `def`.
+* `CONSTRAINT_SCHEMA`: The schema of the constraint.
+* `CONSTRAINT_NAME`: The name of the constraint.
+* `CHECK_CLAUSE`: The clause of the check constraint.
+* `TABLE_NAME`: The name of the table where the constraint is located.
+* `TABLE_ID`: The ID of the table where the constraint is located.