SQL - Having 子句

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  简述

  HAVING Clause使您能够指定过滤哪些组结果出现在结果中的条件。

  WHERE 子句将条件放在选定的列上，而 HAVING 子句将条件放在由 GROUP BY 子句创建的组上。
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  句法

  以下代码块显示了 HAVING 子句在查询中的位置。

  
  SELECT
  FROM
  WHERE
  GROUP BY
  HAVING
  ORDER BY
  

  HAVING 子句必须在查询中的 GROUP BY 子句之后，并且如果使用，还必须在 ORDER BY 子句之前。以下代码块具有 SELECT 语句的语法，包括 HAVING 子句 -

  
  SELECT column1, column2
  FROM table1, table2
  WHERE [ conditions ]
  GROUP BY column1, column2
  HAVING [ conditions ]
  ORDER BY column1, column2
  

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  例子

  考虑具有以下记录的 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 |
  +----+----------+-----+-----------+----------+
  

  以下是一个示例，它将显示大于或等于 2 的相似年龄计数的记录。

  
  SQL > SELECT ID, NAME, AGE, ADDRESS, SALARY
  FROM CUSTOMERS
  GROUP BY age
  HAVING COUNT(age) >= 2;
  

  这将产生以下结果 -

  +----+--------+-----+---------+---------+
  | ID | NAME   | AGE | ADDRESS | SALARY  |
  +----+--------+-----+---------+---------+
  |  2 | Khilan |  25 | Delhi   | 1500.00 |
  +----+--------+-----+---------+---------+