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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
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.
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what is the use of declare keyword
If two relations R and S are joined, then the non matching tuples of both R and S are ignored in __________________.
Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,
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