Question

当我在mysql存储过程下运行时，我得到三个不同的表作为输出。有没有办法，我可以将这三个表和显示输出组合在一个具有不同列和单行的表中吗？

    CREATE DEFINER=`root`@`localhost` PROCEDURE `retrieveApplicantStatus`(IN in_userId INT)
BEGIN
    SELECT applicants_id, approval FROM applicants WHERE users_id = in_userId;

    SELECT pass_fail.result AS test_result, pass_fail.license_approval FROM pass_fail WHERE user_id = in_userId;

    SELECT result AS trial_result FROM trial_result WHERE user_id = in_userId;
END

必需输出：

--------------------------------------------------------------------------
applicants_id | approval | test_result | trial_result | license_approval |
--------------------------------------------------------------------------
              |          |             |              |                  |
--------------------------------------------------------------------------

Answer 1

如果user_id在每个表格中被限制为唯一，那么您可以使用：

CREATE DEFINER=`root`@`localhost` PROCEDURE `retrieveApplicantStatus`(IN in_userId INT)
BEGIN
    SELECT  u.in_userId,
            a.applicants_id, 
            a.approval,
            pf.result AS test_result, 
            pf.license_approval,
            tr.result AS trial_result
    FROM    (SELECT in_userId) AS u
            LEFT JOIN applicants AS a
                ON a.users_id = u.in_userId
            LEFT JOIN pass_fail AS pf
                ON pf.user_id = u.in_userId
            LEFT JOIN trial_result AS tr
                ON tr.user_id = u.in_userId;
END

HOWEVER 如果它不被限制为唯一，那么这将给你一个笛卡尔积，即每个表中的2行总共会给你8行，每个表中的3行会给你27行结果。

Answer 2

尝试使用以下代码： -

BEGIN
    SELECT applicants_id, approval 
    FROM applicants WHERE users_id = in_userId;
        UNIION ALL
    SELECT pass_fail.result AS test_result, pass_fail.license_approval 
    FROM pass_fail 
    WHERE user_id = in_userId;
        UNION ALL
    SELECT result AS trial_result 
    FROM trial_result 
    WHERE user_id = in_userId;
END

存储过程组合结果集

2 个答案: