Table handling, Database Management System

Table Handling

 In RDBMS more than one table can be tackled at a time by using join operation. Join operation is a relational operation that causes 2 tables with a common domain to be joined into a single table or view. SQL states a join implicitly by referring the matching of common columns over which tables are connected in a WHERE clause. Two tables may be connected when each haves a column that shares a common domain with the other. The result of join operation is to be called a single table. Selected columns from all the tables are contained. Every row returned contains data from rows in the dissimilar input tables where values for the common columns match. A vital rule of table handling is that there should be one condition within the WHERE clause for every pair of tables being joined. Therefore if two tables are to be combined, one condition would be essential, but if three tables (X, Y, Z) are to be combined then two conditions would be necessary because there are two pairs of tables (X-Y and Y-Z) OR (X-Z and Y-Z), and so forth. There are various possible types of joins in relational database queries. Four types of join operations are define below:

 

Posted Date: 3/11/2013 2:34:00 AM | Location : United States







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