My SQL 动态查询执行并将输出输出到存储过程中的变量中

Posted 2023-02-24

【中文标题】My SQL 动态查询执行并将输出输出到存储过程中的变量中

【英文标题】：My SQL Dynamic query execute and get ouput into a variable in stored procedure

【发布时间】：2011-08-01 06:30:32

【问题描述】：

我在 My sql 存储过程中生成了一个动态查询。我想将此查询的结果放入 out 参数中。如何做到这一点？

CREATE PROCEDURE 'searchInvoice'
(
  OUT numOfRecords INT
)
BEGIN
  DECLARE query1 TEXT; 
  DECLARE query2 TEXT; 

 SET query1 = 'SELECT COUNT(*) bla bla bla.....'; 
 // Query1 to select the count of matching tuples..

 SET query2 = 'SELECT * from bla bla bla....';
 // Query2 to select original records...

 // later part of this both queries generate dynamically according to some IN parameters..

 // now I wanna assign the output of the query1 into numOfRecords 
 // and I wanna execute the query2 as well.. like this

    SET @Sql = query2;        
    PREPARE STMT FROM @Sql; 
    EXECUTE STMT; 
    DEALLOCATE PREPARE STMT;

 // output of the query2 can be read in php

END

如何将 query1 的输出转换为 OUT 参数(numOfRecords) ??

【参考方案1】：

看看这个例子 -

CREATE TABLE table1(
  column1 VARCHAR(255) DEFAULT NULL,
  column2 VARCHAR(255) DEFAULT NULL,
  column3 VARCHAR(255) DEFAULT NULL
);

INSERT INTO table1 VALUES 
  ('1', 'value1', 'value2'),
  ('2', 'value3', 'value4');

DELIMITER $$
CREATE PROCEDURE procedure1(IN Param1 VARCHAR(255), OUT Param2 VARCHAR(255), OUT Param3 VARCHAR(255))
BEGIN
  SET @c2 = '';
  SET @c3 = '';
  SET @query = 'SELECT column2, column3 INTO @c2, @c3 FROM table1 WHERE column1 = ?';
  PREPARE stmt FROM @query;
  SET @c1 = Param1;
  EXECUTE stmt USING @c1;
  DEALLOCATE PREPARE stmt;
  SET Param2 = @c2;
  SET Param3 = @c3;
END$$
DELIMITER ;

-- Call procedure and use variables
SET @Param1 = 2;
SET @Param2 = '';
SET @Param3 = '';
CALL procedure1(@Param1, @Param2, @Param3);
SELECT @Param2, @Param3;
+---------+---------+
| @Param2 | @Param3 |
+---------+---------+
| value3  | value4  |
+---------+---------+

【讨论】：

@Devart 如果获取多条记录，如何存储在临时表中？

【参考方案2】：

select count(*) into @numOfRecords from .... 

你必须在存储过程中声明变量

希望我已经理解了你的问题。