mysql存储过程怎么接收select结果？

Question

DELIMITER ;;
CREATE PROCEDURE total_num(
IN p_begin INT,
IN p_end INT
)  
BEGIN  
    DECLARE v_begin INT DEFAULT 0;
    DECLARE v_end INT DEFAULT 0;
    DECLARE v_total INT DEFAULT 0;
    DECLARE item_count INT DEFAULT 0;
    
    SET v_begin = p_begin;
    SET v_end = p_end;
    
    WHILE v_begin<=v_end DO 
    SET @table_name = CONCAT('rd_feed_relation_',v_begin);
    SELECT COUNT(1) INTO item_count FROM @table_name;
    SET v_total = v_total + item_count;
    SET v_begin = v_begin+1;
    END WHILE;
    SELECT v_total;
END ;;
DELIMITER ;

CALL total_num(0,3);

这个存储过程为了解决我有几百张表，通过循环count找到这些表记录的总和这个问题。

以上是理想的状态，但是这样的语法是不成立的，找了半天的资料，发现通过CONCAT字段没问题，通过CONCAT后的表名是需要EXECUTE一遍的，这就让我遍历的结果集会是返回多个的，达不到求总数的要求。我该怎么修改这段代码？

Answer 1

已经解决，还是使用了EXECUTE去执行sql，之前多个结果集可能因为没有通过INTO到item_count来获取总数。

DROP PROCEDURE IF EXISTS total_num;  

DELIMITER ;;
CREATE PROCEDURE total_num(
IN p_begin INT,
IN p_end INT
)  
BEGIN  
    DECLARE v_begin INT DEFAULT 0;
    DECLARE v_end INT DEFAULT 0;
    DECLARE v_total INT DEFAULT 0;
    DECLARE item_count INT DEFAULT 0;
    
    SET v_begin = p_begin;
    SET v_end = p_end;
    
    WHILE v_begin<=v_end DO 
    SET @table_name = CONCAT('rd_feed.rd_feed_relation_',v_begin);
    SET @sql = CONCAT("SELECT COUNT(1) INTO @item_count FROM ",@table_name);
    
    PREPARE selectIT FROM @sql;
    EXECUTE selectIT ;
    
    SET v_total = v_total + @item_count;
    SET v_begin = v_begin+1;
    END WHILE;
    DEALLOCATE PREPARE selectIT;
    SELECT v_total;
END ;;
DELIMITER ;

CALL total_num(0,10);

Answer 2

最好用函数接受返回结果

Answer 3

DROP PROCEDURE IF EXISTS total_num;

CREATE PROCEDURE total_num(
IN p_begin INT,
IN p_end INT
)  
BEGIN  
    DECLARE v_begin INT DEFAULT 0;
    DECLARE v_end INT DEFAULT 0;
    DECLARE v_total INT DEFAULT 0;
    
    SET v_begin = p_begin;
    SET v_end = p_end;
    
    WHILE v_begin<=v_end DO 
      SET @sql = CONCAT('SELECT COUNT(1) INTO @item_count FROM rd_feed_relation_', v_begin);

          PREPARE stmt FROM @sql;
        EXECUTE stmt;
      SET v_total = v_total + @item_count;

      SET v_begin = v_begin+1;
    END WHILE;
    DEALLOCATE PREPARE stmt;

    SELECT v_total;
END