system.constraints

System table containing information about existing constraints in all tables.

Description

Contains information about existing constraints in all tables.

Constraints defined on temporary tables are visible in system.constraints only in the session where they were created. They are shown with an empty database field.

Columns

• database (String) — Database name.
• table (String) — Table name.
• name (String) — Constraint name.
• type (Enum8(‘CHECK’ = 0, ‘ASSUME’ = 1)) — Constraint type.
• expression (String) — Constraint expression.

Example

SELECT * FROM system.constraints LIMIT 2 FORMAT Vertical;

Row 1:
──────
database:    default
table:       hits
name:        check_hits
type:        CHECK
expression:  CounterID > 0

Row 2:
──────
database:    default
table:       hits
name:        assume_positive
type:        ASSUME
expression:  WatchID > 0