count distinct result为0时如何隐藏行(博士后)

m4pnthwp  于 2021-07-29  发布在  Java
关注(0)|答案(3)|浏览(355)

我有这个密码

SELECT "School"."name" AS "School",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'A') AS "A",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'B') AS "B",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'C') AS "C",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'D') AS "D"
FROM "public"."user_tokens"
LEFT JOIN "public"."users" "User" ON "public"."user_tokens"."user_id" = "User"."id"
LEFT JOIN "public"."user_roles" "User_2" ON "public"."user_tokens"."user_id" = "User_2"."user_id"
LEFT JOIN "public"."roles" "Role" ON "User_2"."role_id" = "Role"."id" LEFT JOIN "public"."schools" "School" ON "User_2"."school_id" = "School"."id"
GROUP BY "School"."name"
ORDER BY "B" desc

结果如下:

School         A        B        C         D
--------------------------------------------------
    P            5        6       10         6
    Q            1        0        0         0
    R            2        7        0         6
    S            0        8        9         0

是否可以隐藏包含值“0”的整行?在这种情况下,结果应该是学校p只。
之后,如何计算不含零值的“学校”?对于这种情况,结果应该是1
谢谢您。

n3ipq98p

n3ipq98p1#

GROUP BY "School"."name"
HAVING count... > 0
      and count... > 0
ORDER BY "B" desc
to94eoyn

to94eoyn2#

此外,还可以创建列 A , B , C ,和 D 可通过将查询作为另一个查询的表表达式括起来进行操作 SELECT . 在这外面 SELECT 通过添加筛选 predicate 可以很容易地筛选出行:

WHERE "A" <> 0 and "B" <> 0 and "C" <> 0 and "D" <> 0

因此,您的查询可能如下所示:

SELECT
  *,
  count(*) over() as total_rows
from (
  SELECT "School"."name" AS "School",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'A') AS "A",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'B') AS "B",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'C') AS "C",
        count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'D') AS "D"
  FROM "public"."user_tokens"
  LEFT JOIN "public"."users" "User" ON "public"."user_tokens"."user_id" = "User"."id"
  LEFT JOIN "public"."user_roles" "User_2" ON "public"."user_tokens"."user_id" = "User_2"."user_id"
  LEFT JOIN "public"."roles" "Role" ON "User_2"."role_id" = "Role"."id" LEFT JOIN "public"."schools" "School" ON "User_2"."school_id" = "School"."id"
  GROUP BY "School"."name"
) x
WHERE "A" <> 0 and "B" <> 0 and "C" <> 0 and "D" <> 0
ORDER BY "B" desc

如果您希望避免查询中的表达式冗余,那么这对于更复杂的表达式非常有用。

wsxa1bj1

wsxa1bj13#

你有用处吗 having 从句并重复表达

having count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'A') > 0 and
       count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'B') > 0 and
       count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'C') > 0 and
       count(distinct "User"."id") filter (where "public"."user_tokens"."app_name" = 'D')

尽管postgres允许在 GROUP BY ,它不允许在 HAVING 子句(在我看来,扩展sql标准的一种奇怪的方式)。
现在,您还可以简化和改进查询。首先,你需要火柴,所以用 inner join . 第二,使用表别名。我还去掉了双引号——这是个非常糟糕的主意:

SELECT s.name AS School,
        count(distinct u.id) filter (where ut.app_name = 'A') AS A,
        count(distinct u.id) filter (where ut.app_name = 'B') AS B,
        count(distinct u.id) filter (where ut.app_name = 'C') AS C,
        count(distinct u.id) filter (where ut.app_name = 'D') AS D
FROM "public"."user_tokens" ut JOIN
     "public"."users" u
      ON ut.user_id = u.id JOIN
      "public"."user_roles" ur
      ON ut.user_id = ur.user_id JOIN
      "public"."roles" r
      ON ur.role_id = r.id JOIN
      "public"."schools" s
      ON ur.school_id = s.id
GROUP BY s.name
having count(distinct u.id) filter (where ut.app_name = 'A') > 0 and
       count(distinct u.id) filter (where ut.app_name = 'B') > 0 and
       count(distinct u.id) filter (where ut.app_name = 'C') > 0 and
       count(distinct u.id) filter (where ut.app_name = 'D') 
ORDER BY "B" desc

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