在 postgres 中组合多个查询

Question

我有 2 个问题。查询 1：-

select mr.id,count(ml.id) as labor_cnt 
from mreq Mr 
join mlbr ml on Mr.id = ml.mrid 
where Mr.id in(1235,3355) 
group by Mr.id

查询 2：-

select mr.id,count(mm.id) as mtrial_cnt 
from mreq Mr join mmrm mm on Mr.id = mm.mrid 
where Mr.id in(1235,3355) 
group by Mr.id

尝试使用 union all 但行不通。建议将它们结合起来的任何替代方法。

Answer 1

由于您在两个查询中都按 mr.id 分组，我假设您想要的结果类似于：

 mr.id | labor_cnt | mtrial_cnt
--------------------------------
     1 |         5 |          3
     2 |      null |          6
     3 |         4 |          2
     4 |         3 |       null
...

如果这正是您要查找的内容，那么您可以将查询与常见的 table 表达式结合起来。类似于：

WITH labor as (
  SELECT mr.id AS mrid, count(ml.id) AS labor_cnt
    FROM mreq mr JOIN mlbr ml ON mr.id = ml.mrid
    WHERE mr.id IN (1235, 3355)
  GROUP BY mr.id),

mtrial as (
  SELECT mr.id AS mrid, count(mm.id) AS mtrial_cnt
    FROM mreq mr JOIN mmrm mm ON mr.id = mm.mrid
    WHERE mr.id in (1235, 3355)
  GROUP BY mr.id)

SELECT COALESCE(l.mrid, m.mrid), l.labor_cnt, m.labor_cnt
  FROM labor l FULL OUTER JOIN mtrial m ON mrid
ORDER BY mrid;

编辑添加

您似乎在使用 MySQL，并且 MySQL 不支持常见的 table 表达式。 MySQL 确实支持子查询，所以这可能有效（注意：我还没有验证语法，因为我没有可用的运行 MySQL 实例）：

SELECT COALESCE(l.mrid, m.mrid), l.labor_cnt, m.labor_cnt
  FROM 
    (SELECT mr.id AS mrid, count(ml.id) AS labor_cnt
       FROM mreq mr JOIN mlbr ml ON mr.id = ml.mrid
       WHERE mr.id IN (1235, 3355)
     GROUP BY mr.id) AS labor

    FULL OUTER JOIN

    (SELECT mr.id AS mrid, count(mm.id) AS mtrial_cnt
       FROM mreq mr JOIN mmrm mm ON mr.id = mm.mrid
       WHERE mr.id in (1235, 3355)
     GROUP BY mr.id) AS mtrial

    ON mrid

ORDER BY mrid;

在 postgres 中组合多个查询

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