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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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Creating a Table Syantax: CREATE TABLE ENROLMENT (StudentId SID, Name VARCHAR (30) NOT NULL, CourseId CID, PRIMARY KEY (StudentId, CourseId)) ; Explan
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Usefulness of Data Type In SQL, as in most computer languages, a type can be used for constraining the values that are permitted to be used for some purpose. In particular, i
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