Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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);
Semidifference via NOT IN and a subquery SELECT StudentId FROM IS_CALLED WHERE Name = 'Devinder' AND StudentId NOT IN (SELECT StudentId FROM IS_ENROLLED_ON WHER
"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 b
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
Parameter and Keyword Description: collection_name: This keyword identifies the index-by table, nested table, or varray formerly declared within the present scope. cu
ORIGIN OF EARTH - BIG-BAN G HYPOTHESIS - Origin of life is linked to origin of earth. Cosmos, the Universe originated 10-20 billion years ago by Big Bang (thermonu
THEO R Y OF PANSPERMIA - Arrhenius (1908) postulated the cosmic panspermia theory that claims that organisms existed throughout the universe, and their spores, etc., could
Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,
BEGIN Parameter Description in pl sql: BEGIN: This keyword signals the beginning of the executable section of a PL/SQL block, that contains executable statements. The execut
What are 3 good practices of modeling and/or implementing data warehouses?
WHILE-LOOP The WHILE-LOOP statement relates a condition with the series of statements enclosed by the keywords LOOP and END LOOP, as shown: WHILE condition LOOP sequence_of_sta
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd