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
Develop Data Business Intelligence Project Project Description: We are linking our Microsoft SQL Database to GoodData Business Intelligence. We are seeking somebody who has e

Effect of Anonymous Columns Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is creat

EXIT Statement   You can use the EXIT statement to exit a loop. The EXIT statement has 2 forms: the conditional EXIT WHEN and the unconditional EXIT. With the either form, you

Logical Operators The logical operators AND, NOT, and OR follow the tri-state logic shown in table below. The AND and OR are binary operators; NOT is a unary operator.

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

Using a join on 3 tables, select 5 columns and 10 rows from the 3 tables without the use of a Cartesian product Query: SELECT E.LAST_NAME, E.FIRST_NAME, S.BUILDING, S.BRAN

Assigning and Comparing Collections One collection can be assigned to other by an SELECT, INSERT, UPDATE, or FETCH statement, an assignment statement, or by a subprogram call. A

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

which operation is used if we are interested in only certain columns of a table?

Managing Cursors The PL/SQL uses 2 types of cursors: implicit and explicit. The PL/SQL declares a cursor implicitly for all the SQL data manipulation statements, including th