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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.
SELECT a.column_name, b.column_name...
FROM table1 a, table1 b
WHERE a.common_filed = b.common_field;
NAME | AGE | ADDRESS | SALARY |
---|---|---|---|
Ajaashi | 21 | Hyderabad | 25000 |
Kaushik | 22 | Secunderabad | 32000 |
Maulik | 23 | Mumbai | 56000 |
Nikarsh | 24 | Karnataka | 12000 |
Join this table using SELF JOIN as follows:
SELECT a.name, b.age, a.SALARY
FROM CUSTOMERS a, CUSTOMERS b
WHERE a.SALARY < b.SALARY;
NAME | AGE | SALARY |
---|---|---|
Ajaashi | 22 | 25000 |
Ajaashi | 23 | 25000 |
Kaushik | 23 | 32000 |
Nikarsh | 21 | 12000 |
Nikarsh | 22 | 12000 |
Nikarsh | 23 | 12000 |