Cartesian Join: When a Join condition is invalid or omitted completely, the result is a Cartesian product, in which all combinations of rows are displayed. To avoid a Cartesian product, always include a valid join condition in a “where†clause. To Join ‘N’ tables together, you need a minimum of N-1 Join conditions. Forex: to join four tables, a minimum of three joins is required. This rule may not apply if the table has a concatenated primary key, in which case more than one column is required to uniquely identify each row.
Equi Join: This type of Join involves primary and foreign key relation. Equi Join is also called Simple or Inner Joins.
Non-Equi Joins A Non-Equi Join condition containing something other than an equality operator. The relationship is obtained using an operator other than equal operator (=). The conditions such as <= and >= can be used, but BETWEEN is the simplest to represent Non-Equi Joins.
Outer Joins: Outer Join is used to fetch rows that do not meet the join condition. The outer join operator is the plus sign (+), and it is placed on the side of the join that is deficient in information (Top 50 Oracle Interview Questions and Answers pdf). The Outer Join operator can appear on only one side of the expression, the side that has information missing. It returns those rows from one table that has no direct match in the other table. A condition involving an Outer Join cannot use IN and OR operator
Posted Date:- 2021-10-05 05:14:36
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