1

如果我在多个查询（例如 4 个）之间进行联合，我得到以下信息

结果 ：

id  name    num
13  task1   0
13  task1   7102

如果 union 语句中有多个具有相同 id 的记录，如何仅获取num 大于 0的唯一记录。

foreach 
SELECT DISTINCT a.task_code,
                a.task_name ,
                0 AS cand_num INTO ll_task_code ,
                                   ls_task_name,
                                   ll_cand_num
FROM rmtask a,
     rmtaskstate b,
     rmstateuser c
WHERE (a.task_code = b.task_code)
  AND (b.state_code = c.state_code)
  AND (c.emp_num = al_emp_num)
  AND (al_new_flag = 0
       OR (al_new_flag = 1
           AND b.new_flag = 1))
UNION --candidate

SELECT DISTINCT a.task_code,
                a.task_name ,
                cand.emp_num
FROM rmtask a,
     rmtaskstate b,
     rmstateuser c ,
     rmcandidate cand
WHERE (a.task_code = b.task_code)
  AND (b.state_code = c.state_code)
  AND (c.emp_num = cand.emp_num)
  AND (al_new_flag = 0
       OR (al_new_flag = 1
           AND b.new_flag = 1))
  AND (cand.task_code = b.task_code)
  AND (cand.emp_num_candidate = al_emp_num)
  AND (cand.from_date <= DATE(CURRENT))
  AND (cand.to_date >= DATE(CURRENT)
       OR cand.to_date IS NULL)
UNION
SELECT DISTINCT a.task_code,
                a.task_name ,
                0 AS cand_num
FROM rmtask a,
     rmtaskstate b,
     rmstategroup c
WHERE (a.task_code = b.task_code) )
UNION --candidate

SELECT DISTINCT a.task_code,
                a.task_name ,
                cand.emp_num
FROM rmtask a,
     rmtaskstate b,
     rmstategroup c ,
     rmcandidate cand
WHERE (a.task_code = b.task_code)
  AND (b.state_code= c.state_code)
  AND (al_new_flag = 0
       OR (al_new_flag = 1
           AND b.new_flag = 1))
  AND (((c.group_type = 0))
       OR ((c.group_type = 1)
           AND (c.group_code =
                  (SELECT x.degree_code
                   FROM hr_l x
                   WHERE x.emp_num = cand.emp_num
                     AND x.degree_date =
                       (SELECT max(xx.degree_date)
                        FROM hm xx
                        WHERE xx.emp_num = x.emp_num))))
       OR ((c.group_type = 2)
           AND (c.group_code =
                  (SELECT y.title_code
                   FROM ht y
                   WHERE y.emp_num = cand.emp_num
                     AND y.title_date =
                       (SELECT max(yy.title_date)
                        FROM ht yy
                        WHERE yy.emp_num = y.emp_num))))
       OR ((c.group_type = 3)
           AND (1 = r_boss(cand.emp_num)))
       OR ((c.group_type = 4)
           AND (0 <
                  (SELECT count(*)
                   FROM ht x
                   WHERE x.emp_num = cand.emp_num
                     AND x.perm_flag = 1)))
       OR ((c.group_type = 5)
           AND (0 <
                  (SELECT count(*)
                   FROM hm x
                   WHERE x.emp_num = cand.emp_num
                     AND x.vac_flag = 1)))
       OR ((c.group_type = 6)
           AND (0 <
                  (SELECT count(*)
                   FROM hm x
                   WHERE x.emp_num = cand.emp_num
                     AND x.mission_flag = 1))))
  AND (cand.task_code = b.task_code)
  AND (cand.emp_num_candidate = al_emp_num)
  AND (cand.from_date <= DATE(CURRENT))
  AND (cand.to_date >= DATE(CURRENT)
       OR cand.to_date IS NULL) RETURN ll_task_code ,
                                       ls_task_name,
                                       ll_cand_num WITH resume ;
end foreach;
4

2 回答 2

1

如果只有一行num != 0，或者您只需要一个结果，则将现有查询放在子查询中并使用GROUP BY和聚合将被指示：

select id,name,MAX(num) as num
from
   (
       select id,name,num from abc
       union
       select id,name,num from def
       union
       select id,name,num from ghi
   ) as t
group by id,name
于 2013-01-31T10:47:39.500 回答
1
  1. 在 FROM 子句中使用 JOIN 表示法而不是逗号列表。
  2. 我们集会不需要查看您的所有查询即可给出答案；工会的两个部分就足够了。
  3. 您没有提到您正在使用的 Informix 版本，这可能会有所不同。
  4. 如果您的示例输出与您编写的 SQL 相关联会更容易。您的示例输出使用id, name, num，但 SQL 似乎使用task_code,task_name和cand_num。
  5. 您似乎想要给定任务代码和任务名称的最大候选数。

所以，写这样的查询：

SELECT u.task_code, u.task_name, MAX(u.cand_num)
  FROM (SELECT DISTINCT a.task_code, a.task_name, 0 AS cand_num
          FROM rmtask a
          JOIN rmtaskstate b ON a.task_code = b.task_code
          JOIN rmstateuser c ON b.state_code = c.state_code
         WHERE (c.emp_num = al_emp_num)
           AND (al_new_flag = 0 OR (al_new_flag = 1 AND b.new_flag = 1))
        UNION
        SELECT DISTINCT a.task_code, a.task_name, cand.emp_num
          FROM rmtask a
          JOIN rmtaskstate b ON a.task_code = b.task_code
          JOIN rmstateuser c ON b.state_code = c.state_code
          JOIN rmcandidate cand ON c.emp_num = cand.emp_num
         WHERE (al_new_flag = 0 OR (al_new_flag = 1 AND b.new_flag = 1))
           AND (cand.task_code = b.task_code)
           AND (cand.emp_num_candidate = al_emp_num)
           AND (cand.from_date <= DATE(CURRENT))
           AND (cand.to_date >= DATE(CURRENT) OR cand.to_date IS NULL)
       ) AS u
 GROUP BY u.task_code, u.task_name;

显然，您可以在子查询中添加其他替代 UNION 分支。

于 2013-02-01T06:08:35.083 回答