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  • Alias

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    Alias is basically renaming a table temporarily for a sql statement.

    The rename is done only for a particular statement is temporory.

    ex

    The syntax of table alias is as follows

    SELECT column1, column2....
    FROM table_name AS alias_name
    WHERE [condition];

    The syntax of column alias is as follows

    SELECT column_name AS alias_name FROM table_name WHERE [condition];

    ex

    take two table

     ID | NAME     | AGE | ADDRESS   | SALARY   |
    +----+----------+-----+-----------+----------+
    |  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
    |  2 | Khilan   |  25 | Delhi     |  1500.00 |
    |  3 | kaushik  |  23 | Kota      |  2000.00 |
    |  4 | Chaitali |  25 | Mumbai    |  6500.00 |
    |  5 | Hardik   |  27 | Bhopal    |  8500.00 |
    |  6 | Komal    |  22 | MP        |  4500.00 |
    |  7 | Muffy    |  24 | Indore    | 10000.00

    and

    +-----+---------------------+-------------+--------+
    |OID  | DATE                | CUSTOMER_ID | AMOUNT |
    +-----+---------------------+-------------+--------+
    | 102 | 2009-10-08 00:00:00 |           3 |   3000 |
    | 100 | 2009-10-08 00:00:00 |           3 |   1500 |
    | 101 | 2009-11-20 00:00:00 |           2 |   1560 |
    | 103 | 2008-05-20 00:00:00 |           4 |   2060 |
    +-----+---------------------+-------------+--------+

    alias

    SQL> SELECT C.ID, C.NAME, C.AGE, O.AMOUNT FROM CUSTOMERS AS C, ORDERS AS O WHERE C.ID = O.CUSTOMER_ID;

    this show

    +----+----------+-----+--------+
    | ID | NAME     | AGE | AMOUNT |
    +----+----------+-----+--------+
    |  3 | kaushik  |  23 |   3000 |
    |  3 | kaushik  |  23 |   1500 |
    |  2 | Khilan   |  25 |   1560 |
    |  4 | Chaitali |  25 |   2060 |
    +----+----------+-----+--------+

    now for the column

    SQL> SELECT ID AS CUSTOMER_ID, NAME AS CUSTOMER_NAME FROM CUSTOMERS WHERE SALARY IS NOT NULL;

    now result is

    +-------------+---------------+
    | CUSTOMER_ID | CUSTOMER_NAME |
    +-------------+---------------+
    |           1 | Ramesh        |
    |           2 | Khilan        |
    |           3 | kaushik       |
    |           4 | Chaitali      |
    |           5 | Hardik        |
    |           6 | Komal         |
    |           7 | Muffy         |
    +-------------+---------------+

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