MySQL中join的7种方法

join查询的7中方法

• 手写顺序：

  SELECT DISTINCT
    <select_list>
  FROM
    <left_table> <join_type>
  JOIN <right_table> ON <join_condition>
  WHERE
    <where_condition>
  GROUP BY
    <group_by_list>
  HAVING
    <having_condition>
  ORDER BY
    <order_by_condition>
  LIMIT <limit_number>
  

• MySQL执行顺序

  FROM <left_table>
  ON <join_condition>
  <join_type> JOIN <right_table>
  WHERE <where_condition>
  GROUP BY <group_by_list>
  HAVING <having_condition>
  DISTINCT <select_list>
  ORDER BY <order_by_condition>
  LIMIT <limit_number>
  

  

• join连接方式：

  • 内连接：

    

  SELECT <select_list> FROM TableA A INNER JOIN TableB B ON A.Key = B.Key

  
  - 左连接：
  
  ![](https://img2020.cnblogs.com/blog/1644171/202003/1644171-20200314113234405-815784414.png)
  
  ```mysql
  SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key
  

  • 右连接：

    

  SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key

  
  - 只有A
  
  ![](https://img2020.cnblogs.com/blog/1644171/202003/1644171-20200314113312810-147549149.png)
  
  ```mysql
  SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key WHERE B.Key IS NULL
  

• 只有B

  

    SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key WHERE A.Key IS NULL
  

  • 全连接

    

    # MySQL没有FULL OUTER语法。
    SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key
    union
    SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key;
    

  • A，B各自独有：

    ?

  # MySQL没有FULL OUTER语法。
  SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key WHERE B.Key IS NULL
  union
  SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key WHERE A.Key IS NULL;
  

MySQL中join的7种方法

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