CHECK Constraint Column Attribute - Advanced SQL Engine - Teradata Database

An optionally named simple boolean conditional expression used to constrain the values that can be inserted into, or updated for, a column.

A column attribute CHECK constraint cannot reference other columns in the same table or another table.

When you specify multiple CHECK constraints on a single column:

• Multiple unnamed column-level CHECK constraints are combined into a single column-level CHECK constraint.
• Multiple named column-level CHECK constraints are processed individually.

You can specify column-level CHECK constraints for nontemporal and temporal tables. See Teradata Vantage™ - ANSI Temporal Table Support , B035-1186 and Teradata Vantage™ - Temporal Table Support , B035-1182 .

CHECK (boolean_condition)

The boolean_condition must reference a column_name.

For an unnamed CHECK column constraint, use this syntax:

     CHECK (boolean_condition)

CONSTRAINT constraint_name

For a named CHECK column constraint, use this syntax:

     CONSTRAINT constraint_name CHECK (boolean_condition)

Example: Specifying a Mix of Column-Level and Table-Level Named and Unnamed CHECK Constraints

The request in this example combines the three unnamed CHECKs for column_1. Constraint check_0 and each of the named CHECKs for column_2 are treated as table constraints.

    CREATE TABLE good_4 (
      column_1 INTEGER
        CHECK (column_1 > 0)
        CHECK (column_1 < 999)
        CHECK (column_1 NOT IN (100,200,300))
       CONSTRAINT check_0
        CHECK (column_1 IS NOT NULL),
      column_2 INTEGER
       CONSTRAINT check_1
        CHECK (column_2 > 0)
        CHECK (column_2 < 999));