Note
This view is available starting with V1.4.
Purpose
This view displays the constraint information of keys in a column.
Columns
Column |
Type |
Nullable |
Description |
|---|---|---|---|
| CONSTRAINT_CATALOG | varchar(3) | NO | Fixed value (def). |
| CONSTRAINT_SCHEMA | varchar(128) | NO | The name of the database. |
| CONSTRAINT_NAME | varchar(7) | NO | The name of the constraint, which can be PRIMARY, a column name, or a foreign key name. |
| TABLE_CATALOG | varchar(3) | NO | The table catalog. |
| TABLE_SCHEMA | varchar(128) | NO | The name of the database. |
| TABLE_NAME | varchar(256) | NO | The name of the table. |
| COLUMN_NAME | varchar(128) | NO | The name of the column. |
| ORDINAL_POSITION | bigint(20) | NO | The sequence number of the column in the primary key constraint, starting from 1. |
| POSITION_IN_UNIQUE_CONSTRAINT | null | NO | For unique and primary key constraints, the sequence number of the column in the constraint definition; for foreign key constraints, the sequence number of the key in the referenced table. |
| REFERENCED_TABLE_SCHEMA | varchar(128) | NO | Default value: NULL. |
| REFERENCED_TABLE_NAME | varchar(256) | NO | Default value: NULL. |
| REFERENCED_COLUMN_NAME | varchar(128) | NO | Default value: NULL. |
Sample query
Query the constraint information of keys in the tbl4 table.
obclient [oceanbase]> SELECT * FROM information_schema.KEY_COLUMN_USAGE WHERE TABLE_NAME='tbl4';
The query result is as follows:
+--------------------+-------------------+----------------------------+---------------+--------------+------------+-------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_CATALOG | TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | ORDINAL_POSITION | POSITION_IN_UNIQUE_CONSTRAINT | REFERENCED_TABLE_SCHEMA | REFERENCED_TABLE_NAME | REFERENCED_COLUMN_NAME |
+--------------------+-------------------+----------------------------+---------------+--------------+------------+-------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+
| def | infotest | tbl4_OBFK_1736909788672362 | def | infotest | tbl4 | col2 | 1 | 1 | infotest | tbl2 | col1 |
+--------------------+-------------------+----------------------------+---------------+--------------+------------+-------------+------------------+-------------------------------+-------------------------+-----------------------+------------------------+
1 row in set