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极客学院团队出品 · 更新于 2018-04-21 19:00:48

SQL 对结果进行排序

SQL ORDER BY 子句根据一列或者多列的值,按照升序或者降序排列数据。某些数据库默认以升序排列查询结果。

语法:

用于将结果按照升序或者降序排列的 ORDER BY 子句的基本语法如下所示:

    SELECT column-list 
    FROM table_name 
    [WHERE condition] 
    [ORDER BY column1, column2, .. columnN] [ASC | DESC];

ORDER BY 子句可以同时使用多个列作为排序条件。无论用哪一列作为排序条件,都要确保该列在存在。

示例:

考虑含有如下所示记录的 CUSTOMERS 表:

    +----+----------+-----+-----------+----------+
    | 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 |
    +----+----------+-----+-----------+----------+

下面的例子将查询结果按照 NAME 和 SALARY 升序排列:

    SQL> SELECT * FROM CUSTOMERS
         ORDER BY NAME, SALARY;

结果如下所示:

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

下面的例子将查询结果按照 NAME 降序排列:

    SQL> SELECT * FROM CUSTOMERS
         ORDER BY NAME DESC;

结果如下所示:

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

以自定义的方式排序查询结果的 SELECT 语句如下所示:

    SQL> SELECT * FROM CUSTOMERS
        ORDER BY (CASE ADDRESS
        WHEN 'DELHI'     THEN 1
        WHEN 'BHOPAL'    THEN 2
        WHEN 'KOTA'      THEN 3
        WHEN 'AHMADABAD' THEN 4
        WHEN 'MP'   THEN 5
        ELSE 100 END) ASC, ADDRESS DESC;

结果如下所示:

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

这样查询结果就会先以你所定义的顺序按照 ADDRESS 排列。对于其余的 ADDRESS 值,查询结果仍然按照自然方式排列。亦即,除列出的 ADDERSS 之外,其余的 ADDRESS 按照字母表的逆序排列。

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