Author: admin
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Oracle SELF JOIN
Self Join is a specific type of Join. In Self Join, a table is joined with itself (Unary relationship). A self join simply specifies that each rows of a table is combined with itself and every other row of the table. Syntax Oracle SELF JOIN Example Let’s take a table “customers”. Join this table using…
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Oracle EQUI JOIN
Oracle Equi join returns the matching column values of the associated tables. It uses a comparison operator in the WHERE clause to refer equality. Syntax Equijoin also can be performed by using JOIN keyword followed by ON keyword and then specifying names of the columns along with their associated tables to check equality. Syntax Oracle…
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Oracle OUTER JOIN
An outer join is similar to equijoin but it gets also the non-matched rows from the table. It is categorized in Left Outer Join, Right Outer Join and Full Outer Join by Oracle 9i ANSI/ISO 1999 standard. Left Outer Join Left Outer Join returns all rows from the left (first) table specified in the ON…
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Oracle INNER JOIN
Inner Join is the simplest and most common type of join. It is also known as simple join. It returns all rows from multiple tables where the join condition is met. Syntax Image representation of Inner Join Oracle INNER JOIN Example Let’s take an example to perform Inner Join on two tables “Suppliers” and “Order1”.…
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Oracle Joins
Join is a query that is used to combine rows from two or more tables, views, or materialized views. It retrieves data from multiple tables and creates a new table. Join Conditions There may be at least one join condition either in the FROM clause or in the WHERE clause for joining two tables. It…
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Hierarchy Operator
Purpose: Used to query hierarchical data using a parent-child relationship.Syntax: Example: Explanation: This retrieves a hierarchy of employees starting from those without a manager (top level).
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Set Operators
Operators: Example: Explanation: This retrieves unique first names from both the employees and managers tables.
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Concatenation Operator
Purpose: Combines two or more strings into one.Operator: Example: Explanation: This creates a full name by concatenating first_name and last_name.
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NULL Operator
Purpose: Tests for NULL values in a column. Syntax or Example: Explanation: This retrieves employees who do not belong to any department.