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
COSMOZOI C THEORY - Richter (1865) proposed the cosmozoic theory that says that life came by spores (cosmozoa) or other particles from other planets on the earth.

Great Plains (Microsoft Dynamics) Purchases Report Project Description: I want to build a purchases report that matches the General Ledger. presently, when I join the PM20

How Exceptions Propagate ? Whenever an exception is raised, and if the PL/SQL cannot find a handler for it in the present subprogram or block, the exception propagates. That is

Delimiters A delimiter is a simple or compound symbol which has a special meaning to PL/SQL. For example, you use delimiters to symbolize an arithmetic operation like additio

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

1. a. Write a trigger that fires when a part's price is updated. The trigger will write a record into a table called PriceUpdates. The record should contain the information of

DELETE Command - SQL Loosely speaking, DELETE removes some existing rows from its target table. Suppose the university decides that course C3 is to be withdrawn. Example shows

EXECUTE IMMEDIATE Statement   The EXECUTE IMMEDIATE statement prepare (parses) and instantly executes a dynamic SQL statement or an anonymous PL/SQL block. Syntax:

Opening a Cursor Opening the cursor executes the query & identifies the result set that consists of all rows that meet the query search criteria. For the cursors declared usin

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