Semidifference and NOT - SQL

In this section first describe the relational difference operator, named MINUS. Example here shows SQL's closest counterpart of that operator.

Example: Difference in SQL

SELECT StudentId

FROM IS_CALLED

WHERE Name = 'Devinder'

EXCEPT DISTINCT CORRESPONDING

SELECT StudentId

FROM IS_ENROLLED_ON

WHERE CourseId = 'C1'

The syntax for  EXCEPT exactly parallels that for  UNION. The key words  DISTINCT, ALL, and CORRESPONDING have exactly the same significance as in UNION, and DISTINCT remains the default option. When CORRESPONDING is not given, columns are paired by ordinal position, as in UNION.