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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_take_exam_alternative2
CHECK (EXISTS (SELECT StudentId, CourseId
FROM IS_ENROLLED_ON
WHERE StudentId = EXAM_MARK.StudentId
AND CourseId = EXAM_MARK.CourseId)
) ;
In Example, note the use of the table name, EXAM_MARK, as a range variable to qualify references to columns of that table. As always, the condition given as the operand of CHECK is one that would be legal as a WHERE condition following a FROM clause specifying just the table to which the constraint applies (viz., FROM EXAM_MARK in the case at hand).
Procedural Constraint Enforcement (Triggers) SQL has an alternative method of addressing database integrity, involving event-driven procedural code. The special procedures th
Providing Results of Queries Expressing queries in SQL is the (big) subject. Here I present just a simple example to give you the flavour of things to come in those chapters.
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SQL Operators The PL/SQL uses all the SQL set, comparison, and row operators in the SQL statements. This part briefly describes some of these operators. 1. Comparison Opera
Raise_application_error - procedure of package DBMS_STANDARD , allows to issue an user_defined error messages by stored sub-program or database trigger.
BETWEEN and NOT BETWEEN Operator in SQL Example: Restricting exam marks to between 0 and 100 CREATE ASSERTION Marks_between_0_and_100 CHECK (NOT EXISTS (SELECT * FROM
Methods: In normal, a method is a subprogram declared in an object type specification using the keyword MEMBER or STATIC. The method cannot have similar name as the object typ
a. Write an anonymous block that contains a PL/SQL function. Given an order number orderNo, the function will calculate the total number of the parts in the order. Then the anonym
EXECUTE Privilege To call an invoker-rights routine straightforwardly, the users should have the EXECUTE privilege on that routine. By yielding the privilege, you permit a user
This task involves developing some functions that extract data from an SQL database. The scenario is that a company which owns an online vehicle search website wants to generate so
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