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make your own data type
• Some databases such as Postgres allow you to define your own type
• CREATE TYPE: composite, enum, range, base, or shell
• Domain = limited set of possible values
• Examples:
Postal codes for states in US (56)
DayOfWeek… ‘MON’, ‘WED’, ‘FRI’, ‘unknown’
• CREATE DOMAIN color VARCHAR(20)
CHECK ( VALUE IN ( 'pumpkin' , 'periwinkle' , 'seafoam' ) ) ;
• Enforced by the database engine – Invalid data rejected
INSERT INTO tbl ( color_ ) VALUES( 'dusty-rose' ) ;
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