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Use of COUNT in SQL
It describes and discusses various general methods of expressing constraints, eventually noting that support for "=" with relation operands is sufficient for completeness. It also notes that every constraint can be expressed as an invocation of IS_EMPTY, where IS_EMPTY(r) is equivalent to r { } = TABLE_DUM. First, though, it gives Example, showing how to use COUNT to test a relation for emptiness. Example here is a direct translation of that one into SQL.
Example: Testing for absence of counterexamples.
CREATE ASSERTION Must_be_enrolled_to_take_exam
CHECK ((SELECT COUNT (*)
FROM EXAM_MARK
WHERE (Student_Id, CourseId ) NOT IN
(SELECT Student_Id, CourseId
FROM IS_ENROLLED_ON ) )
= 0);
Restriction in SQL Syntax: SELECT DISTINCT StudentId FROM IS_CALLED WHERE Name = 'Boris' The WHERE clause operates on the result of the FROM clause in analogo
Bitmap Join Indexes - This feature will increase the performance and detains the size and format of your databases in data Character Semantics and Globalization -This featur
An analyst in the quality assurance office reviews the time lapse between receiving an order and shipping an order. Any orders that have not been shipped within a day of the order
Transaction Control The Oracle is transaction oriented; that is, Oracle uses the transactions to make sure the data integrity. The transaction is a sequence of SQL data manip
MAX and MIN operator in SQL Example: (SELECT MAX (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') (SELECT MIN (Mark) FROM EXAM_MARK WHERE StudentId = 'S1') Example
Example of Check Constraints Example: Workaround for when subqueries not permitted in CHECK constraints CREATE FUNCTION NO_MORE_THAN_20000_ENROLMENTS ( ) RETURNS BOOLEAN
Parameter & Keyword Description: function_name: The user-defined function is identifying by that keyword. parameter_name: This identifies the formal parameter that
Dynamic SQL: The Most PL/SQL programs do a predictable, specific job. For illustration, a stored procedure may accept an employee number and salary increase, and then update t
Dynamic Ranges The PL/SQL lets you determine the loop range dynamically at run time, as the example below shows: SELECT COUNT(empno) INTO emp_count FROM emp; FOR i IN 1..emp_cou
Why Use Cursor Variables ? Primarily, you use the cursor variables to pass the query result sets between the PL/SQL stored subprograms and different clients. Neither PL/SQL nor
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