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CHECK Constraints in SQL
A CHECK constraint is a table constraint defined using the key word CHECK, as already illustrated in several examples in this chapter. In particular, a CHECK constraint can be used to express a constraint such as the one shown in Example, referred to in the theory book as a tuple constraint (so one might call it a row constraint in SQL). This is clearly the way most SQL users would prefer to express such a constraint.
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Example of Alternative formulation as a table constraint Example: Alternative formulation as a table constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_
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What are the rates for help in writing PL/SQL procedures and functions?
Inner Join We have learned how to retrieve data from one table by using SELECT statement. But, as we have learned, normalized relational databases mean the data is spread betw
Left and Right Joins LEFT OUTER JOIN can be used when you want to retrieve the data from the main table (table1) even if there is no match in other tables (table_2, table_3...
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RETURN Statement The RETURN statement instantly completes the execution of a subprogram and returns control to the caller. The Execution then resumes with the statement below t
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