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"Not Enforced" Table Constraints
A constraint that is not enforced is not really a constraint within the meaning of the act, but SQL does have such a concept and it needs to be mentioned here. With the exception of UNIQUE and PRIMARY KEY specifications, a table constraint can be declared as either ENFORCED (the default option) or NOT ENFORCED. The "enforcement characteristic" of such a constraint can be changed by means of an ALTER TABLE statement. For example, the table constraint MAX_ENROLMENTS becomes not enforced by execution of the statement ALTER TABLE ALTER CONSTRAINT MAX_ENROLMENTS NOT ENFORCED. The immediate effect is the same (ignoring effects on the catalog) as if ALTER TABLE DROP CONSTRAINT MAX_ENROLMENTS had been given. However, it's easier to reinstate the constraint using ALTER TABLE ALTER CONSTRAINT MAX_ENROLMENTS ENFORCED. NOT ENFORCED cannot be specified for domain constraints or assertions, so use of CREATE ASSERTION should really be the preferred method of declaring a constraint, but unfortunately that option is not widely available.
Keyword & Parameter Description: boolean_expression: This is an expression which yields the Boolean value that is TRUE, FALSE, & NULL. character_expression: This
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Task 2 [12 marks] Write the package body for the following package specification (the detailed description of each function and procedure is provided in the appendix below). Place
Using DEFAULT You can use the keyword DEFAULT rather than that of the assignment operator to initialize the variables. For e.g. the declaration blood_type CHAR := ’O’; it can b
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