Use of count in sql, PL-SQL Programming

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);

Posted Date: 1/18/2013 7:26:01 AM | Location : United States







Related Discussions:- Use of count in sql, Assignment Help, Ask Question on Use of count in sql, Get Answer, Expert's Help, Use of count in sql Discussions

Write discussion on Use of count in sql
Your posts are moderated
Related Questions
Set Operators The Set operators combine the results of the two queries into one result. The INTERSECT returns all the distinct rows selected by both queries. The MINUS returns

Parameter and Keyword Description: dynamic_string: This is a string variable, literal, or expression which represents a SQL statement or the PL/SQL block. define_vari

%ISOPEN The %ISOPEN yields TRUE if its cursor or cursor variable is open; or else, the %ISOPEN yields FALSE. In the illustration, you use the %ISOPEN to select an action:

Pass the nulls to a dynamic SQL: Passing Nulls: Assume that you want to pass the nulls to a dynamic SQL statement. For illustration, you may write the EXECUTE IMMEDIATE

Need Azure CRM Web Application with two-factor authentication We presently have a CRM-like database stored on MS Azure that we presently access over an MS Access application. It

Keyword & Parameter Description: PRAGMA: These keywords signify that the statement is a pragma (i.e. compiler directive). The Pragmas are processed at the compile time, n

How Transactions Guard Your Database The transaction is a sequence of SQL data manipulation statements which does a logical unit of work. The Oracle treats the sequence of SQL

Implicit Cursors The Oracle implicitly opens a cursor to process each SQL statement not related with an explicitly declared cursor. The PL/SQL lets you refer to the most recen

At times, Brewbean's has changed the id number for existing products. In the past, they have had to add a new product row with the new id to the BB_PRODUCT table, modify all the co

Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri