cartesian product sql

In this article, the main description of the various connections in SQL and the scope of use, as well as the further interpretation of relational algebra and relational algorithms on the same query in different ways.Introduction to multi-table connectionsIn a relational database, a query tends to involve more than one table, because few have a single table, and if most queries involve only one table, then that table is often lower than the third parad

Tags: style ar using SP for div on art issuesNo join condition results in Cartesian productPeople who have studied linear algebra know that the Cartesian product is popularly said that each member of the two set is associated with a random member of the other party's collection. It can be imagined that, in SQL queries,

Scott.emp;--empno ename Mgr Mgrname--7369 SMITH 7902 FORD--empno ename Mgr Mgrname--7902 FORD 7566 JONES--Multi-table connection--the fastest way to back up a table's data, note that the method simply backs up the data and does not copy the constraintsCREATE TABLE tb_emp as SELECT * from Scott.emp;SELECT * from Tb_emp;SELECT * from Scott.emp;Employee name of employee number E of the--E employee name E of the manager number TSELECT E.empno,e.ename,e.mgr,t.enameFrom Scott.emp e,scott.tb_emp tWHER

What is Cartesian product? The implementation of cartesian products in SQL is not only Cross Join ). All join methods are converted into temporary Cartesian Product tables. Cartesian

Label:In SQL query statements, the Cartesian product operation is often used in the inner joins, outer joins, and the basis of connections. In a simple SQL, maybe we can also distinguish how the data is connected, once the query is complicated, the brain also made a paste, and stumbled. In this paper, we simply record

Cartesian product in SQLWhen we operate on database tables, we often associate multiple tables, and we will certainly not be unfamiliar with multiple table connection queries, but it is easy to come up with huge redundant data.Cartesian product Mathematical ConceptCartesian product refers to a

/* ========================================================Description:Use SQL to implement Cartesian ProductAuthor: CCDate: 2011.11.03======================================================== */ Use Test Go Select * From L; -- Such as l Select * From M; -- Such as m -- Cross-join implementation, lm Select * From L Cross Join M; L table Lid name-------------------------------10

Tags: experience note method Bubuko class style Targe each nameFirst of all, SQL will be used to understand, not experts, the following are working experience, talk to lyric.Today to help verify the port of colleagues published, look at the relevant SQL content, found that its use of SQL statements will lead to Cartesian