Constraints

Question 0

Constraint syntax

Answer 0

CONSTRAINT nameOconstrsaint UNIQUE(column2addconstrainton)

Question 1

Types of constraints

Answer 1

Primary key - ensures each row has a uniqueID

Foreign key - ensures FK points to valid PK

Check constraint - enforces formulas (check clauses) defined on a column.

Unique - no 2 rows can have same unique values.

NOT NULL - does not allow NULL values

Note: there can only be 1 NULL entry