Use of table comparisons - sql, PL-SQL Programming

Use of Table Comparisons - SQL

Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into a value expression of type ROW ( r ) MULTISET, where r is the row type of t. However, the only operator in SQL for comparing two multisets is "=", so SQL has no direct counterparts of examples, which use "⊆", and nor does this chapter.

Those examples are shown merely to demonstrate that every constraint that can be expressed as an invocation of IS_EMPTY can be formulated alternatively as an invocation of "⊆". If SQL were to have a counterpart of that operator, it would presumably have to be an "is submultiset of " operator, where m1 is a submultiset of m2 if and only if each element of m1 appears at least as many times in m2 as it does in m1. But SQL doesn't have such an operator.

Posted Date: 1/18/2013 7:45:28 AM | Location : United States

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

Write discussion on Use of table comparisons - sql
Your posts are moderated
Related Questions
Example of Cast Operator So long as CAST is used as shown, we could obtain the total marks for each exam in similar fashion, using SUM (Mark) AS TotalMarks. However, this giv

What is Cursors how to use it in Real time application ?

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

Remote Operations: As the illustration shows below, the PL/SQL subprograms can execute the dynamic SQL statements which refer to the objects on a remote database: PROCEDURE

Stored Subprograms Normally, tools (like Oracle Forms) which incorporate the PL/SQL engine can store subprograms locally for later, strictly local execution. Though, to become

%FOUND Until the SQL data manipulation statement is executed, the %FOUND yields NULL. Afterward, the %FOUND yields TRUE, when an INSERT, UPDATE, or DELETE statement affected o

Example of Tables within a Table - SQL Example: Obtaining C_ER from COURSE and EXAM_MARK SELECT CourseId, CAST (TABLE (SELECT DISTINCT StudentId, Mark FROM EXAM_MARK AS EM

UTL_FILE: The Package UTL_FILE permits your PL/SQL programs to read & write operating system (OS) text files. It gives a restricted version of the standard OS stream file I/O,

Example of EXCEPT Operator - SQL Example, like its counterpart in the theory book, illustrates the convenience of allowing any table expression to be the source for an INSERT

Nested Tables versus Index-by Tables The Index-by tables and nested tables are just similar. For e.g.  They have similar structure and their individual elements are accessed in