Interesting properties of cross join - sql, PL-SQL Programming

Assignment Help:

Interesting properties of CROSS JOIN - SQL

Compare these with the "interesting properties of JOIN", CROSS JOIN is associative but not commutative. Unlike JOIN and NATURAL JOIN, CROSS JOIN is not idempotent. Let t be any table and let n be its cardinality. Then t CROSS JOIN t has twice as many columns as t and n2 rows. Also unlike JOIN, CROSS JOIN has no identity value. If t is a table, there is no table t0 such that t CROSS JOIN t0 = t. That's because t0 would be required to have no columns and exactly one row, but SQL doesn't recognize the existence of tables with no columns.


Related Discussions:- Interesting properties of cross join - sql

Advantages of invoker rights, Advantages of Invoker Rights The Invoker-...

Advantages of Invoker Rights The Invoker-rights routines centralize the data retrieval. They are particularly helpful in applications which store data in various schemas. In su

Table comparison - sql, Table Comparison - SQL The following definitio...

Table Comparison - SQL The following definitions for relation comparisons: Let r1 and r2 be relations having the same heading. Then: r1 ⊆ r2 is true if every tuple of r1

Using first and last - collection method, Using FIRST and LAST FIRST a...

Using FIRST and LAST FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL

Providing results of queries, Providing Results of Queries Expressing ...

Providing Results of Queries Expressing queries in SQL is the (big) subject. Here I present just a simple example to give you the flavour of things to come in those chapters.

Predicate - sql, Predicate - SQL Consider the declarative sentence-a p...

Predicate - SQL Consider the declarative sentence-a proposition-that is used to introduce this topic:  "Student S1, named Anne, is enrolled on course C1." Recall that th

Remote operations in pl sql, Remote Operations: As the illustration sh...

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

Best practices/Data Warhousing, What are 3 good practices of modeling and/o...

What are 3 good practices of modeling and/or implementing data warehouses?

Referencing records, Referencing Records Unlike the elements in a coll...

Referencing Records Unlike the elements in a collection, that are accessed using subscripts, the fields in a record are accessed by name. To reference an individual field, you

Loop statements, LOOP Statements The LOOP statements execute a series o...

LOOP Statements The LOOP statements execute a series of statements at multiple times. The loops enclose the series of statements that is to be repeated. The PL/SQL provides typ

Effect of anonymous columns, Effect of Anonymous Columns Now, recall t...

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

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd