mysql存储过程 嵌套查询

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DELIMITER $$
CREATE PROCEDURE test_cursor(IN studyId Long)
BEGIN
-- 需要执行的SQL语句
DECLARE v_sql_1 VARCHAR(2000);
DECLARE v_sql_2 VARCHAR(2000);


  /*定义变量*/
DECLARE crf_form_id Long;
DECLARE table_name VARCHAR(255);

DECLARE field_sql VARCHAR(2000);


-- 定义循环标识，默认值为 FALSE
DECLARE done INT DEFAULT FALSE;

  -- 定义游标，并将sql结果集赋值到游标中
DECLARE My_Cursor CURSOR FOR (
select
c.id, c.table_name
from
study s, crf c, study_crf sc
where
s.id=sc.study_id
and c.id=sc.crf_form_id
and s.deleted=0
and c.deleted=0
and c.generate_to_db=1
and c.table_name is not null
and s.id=studyId
   );


  -- 将结束标志绑定到游标，若没有数据返回,程序继续,并将变量done设为TRUE
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;


  -- 打开游标
OPEN My_Cursor;

      myLoop2 : LOOP

      -- 循环游标中的数据，并赋值到变量中
FETCH My_Cursor INTO crf_form_id, table_name ;

IF done THEN
LEAVE myLoop2;

      ELSE

-- 动态拼接sql并赋值v_sql_1
SET v_sql_1 = CONCAT('
select 
GROUP_CONCAT(cdf.field_name, " as \'", f.label, "\'") into @param1
from
crf_dict_field cdf, study_crf sc, dictionary d, field f
where cdf.crf_form_id=sc.crf_form_id
and cdf.dict_id=d.id
and cdf.field_id=f.id
and cdf.deleted=0
and d.deleted=0
and f.deleted=0
and cdf.generate_to_db=1
and cdf.field_name is not null
and cdf.crf_form_id=', crf_form_id, ' and sc.study_id=', studyId
);
-- 需要用@转换下,直接v_sql_1执行不了
SET @sql_1 = v_sql_1;
-- 预处理需要执行的动态SQL，其中stmt是一个变量
PREPARE stmt1 FROM @sql_1; 
-- 执行SQL语句
EXECUTE stmt1;  
-- 释放掉预处理段  
DEALLOCATE PREPARE stmt1;    
-- @param1赋值给maxId2
SET field_sql = @param1;


-- 动态拼接sql并赋值v_sql_2
SET v_sql_2 = CONCAT('select id, objectId, ', field_sql, ' from ', table_name, ' where deleted=0 and objectId in (select so.id from study_object so where so.deleted=0 and so.study_id=', studyId, ') ');
SET @sql_2 = v_sql_2;
-- 预处理需要执行的动态SQL，其中stmt是一个变量
PREPARE stmt2 FROM @sql_2; 
-- 执行SQL语句
EXECUTE stmt2;  
-- 释放掉预处理段  
DEALLOCATE PREPARE stmt2;   



-- 嵌套使用是内部游标结束后给done置 FALSE
SET done=FALSE;

END IF;

    END LOOP myLoop2;

-- 关闭游标
CLOSE My_Cursor;
END
$$
DELIMITER ;