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我的程序：（这是一个计划）

  delimiter //
  CREATE PROCEDURE get_random_data()
  BEGIN
  Declare Count_a INT;
      SELECT Floor(Count(`id_x`) * Rand()) INTO Count_a From `x_data`  Where `ok_w` = 1 And `active` = 2 And `time` >= Unix_timestamp();

   # Now We select Some Rows
   SELECT `id_x` From `x_data` Where `spec` = 1 Limit Count_a,3;

   # And if Count of this select is small than < 3

   IF(row_count() < 3) then
      SELECT `id_anonsu` From `x_data` Where `spec` = 0 Limit Count_a,2;
   END IF ;


  END//
  delimiter ;

// 目标

如何从两个查询中获取结果？// 一个来自 if 语句之前的查询

// 第二个来自语句中的查询，如果第一个查询计数小于 3

4

2 回答 2

1

好的，我找到了答案。

原代码：

   IF(row_count() < 3) then
       SELECT `id_anonsu` From `x_data` Where `spec` = 0 Limit Count_a,2;
   END IF ;

被替换为：

IF(FOUND_ROWS() < 3) THEN SELECT `id_anonsu` From `x_data` Where `spec` = 0 Limit Count_a,2;
END IF ;

更好的版本：

使用查询很好（谁使用限制）并且我们需要知道存储过程中的（查询）返回的行数

带演出次数的版本

    DROP PROCEDURE IF EXISTS test;
    Delimiter //
    CREATE PROCEDURE test(OUT w INT)
    BEGIN
    Declare Counter_a INT DEFAULT 0;


        Set @id_counter = 0;

        SELECT Floor(Count(`id_x`) * Rand()) INTO Counter_a From `x_data`  Where `ok_w` = 1 And `active` = 2 And `time` >= Unix_timestamp();

        SELECT @id_counter := @id_counter + 1, `id_x` From `x_data` Where `spec` = 1 Limit Counter_a,3;


        IF @id_counter < 3 THEN 
            Set Counter_a = Counter_a + 1;
            SELECT `id_x` From `x_data` Limit Counter_a,2;


        END IF;

        Set w = @id_counter;


    END //
    Delimiter ;

输出如下：

  mysql> Call test(@z); Select @z;
  +--------------------------------+-----------+
  | @id_counter := @id_counter + 1 |   id_x    |
  +--------------------------------+-----------+
  |                              1 |         7 |
  |                              2 |         8 |
  +--------------------------------+-----------+
  2 rows in set (0.00 sec)

  +-----------+
  |   id_x    |
  +-----------+
  |         8 |
  +-----------+
  1 row in set (0.01 sec)

  Query OK, 0 rows affected (0.01 sec)

  +------+
  | @z   |
  +------+
  |    2 |
  +------+
  1 row in set (0.00 sec)

隐藏计数的版本

    DROP PROCEDURE IF EXISTS test;
    Delimiter //
    CREATE PROCEDURE test(OUT w INT)
    BEGIN
    Declare Counter_a INT DEFAULT 0;


        Set @id_counter = 0;

        SELECT Floor(Count(`id_x`) * Rand()) INTO Counter_a From `x_data`  Where `ok_w` = 1 And `active` = 2 And `time` >= Unix_timestamp();

        SELECT `id_x` From `x_data` Where @id_counter := @id_counter + 1 And `spec` = 1 Limit Counter_a,3;


        IF @id_counter < 3 THEN 
            Set Counter_a = Counter_a + 1;
            SELECT `id_x` From `x_data` Limit Counter_a,2;


        END IF;

        Set w = @id_counter;


    END //
    Delimiter ;

输出如下：

  mysql> Call test(@z); Select @z;
  +-----------+
  |   id_x    |
  +-----------+
  |         7 |
  |         8 |
  +-----------+
  2 rows in set (0.00 sec)

  +-----------+
  |   id_x    |
  +-----------+
  |         8 |
  +-----------+
  1 row in set (0.01 sec)

  Query OK, 0 rows affected (0.01 sec)

  +------+
  | @z   |
  +------+
  |    2 |
  +------+
  1 row in set (0.00 sec)

@小费

 @id_counter := @id_counter + 1

它必须在 where 的所有条件之前。

例如：

[.....] Where @id_counter := @id_counter + 1 And `field_2` > 1 LIMIT 0, 5;

将永远返回 1...

正确版本

[.....] Where `field_2` > 1 And  [Other conditions] And @id_counter := @id_counter + 1  LIMIT 0, 5;
于 2012-12-15T10:17:41.347 回答
1

这取决于您使用的客户端界面。例如 JDBC 有 statement.getMoreResults()

有趣的是，查询同时包含分隔符 // 和 // 注释。

于 2012-12-15T09:58:34.780 回答