Mysql 返回连接表不正确值的行数

Question

大家好。我正在努力从 tables 的数据库中检索数据。

我的查询如下所示。

SELECT DISTINCT applicable_areas.area, applicable_areas.id as id,  count(distinct supreme_applicable_areas.applicable_area_id) as supreme_court_cases, count(distinct appeal_applicable_areas.applicable_area_id) as appeal_court_cases
FROM `applicable_areas`
JOIN appeal_applicable_areas ON appeal_applicable_areas.applicable_area_id = applicable_areas.id
JOIN supreme_applicable_areas ON supreme_applicable_areas.applicable_area_id = applicable_areas.id
JOIN cp_cases_counsel ON ( (cp_cases_counsel.suitno = supreme_applicable_areas.suitno) OR (cp_cases_counsel.suitno = appeal_applicable_areas.suitno)) 
WHERE cp_cases_counsel.counsel_id = 54
GROUP BY applicable_areas.area, applicable_areas.id
ORDER BY applicable_areas.area ASC;

它似乎检查 'supreme_applicable_areas' table 中是否出现值，如果找到，则继续检查 'appeal_applicable_areas' table 中的值.所以，如果没有supreme的价值，但是有上诉的价值，它带来了supreme和上诉的结果。但是我希望它选择一个。

有办法实现吗？

提前致谢

Answer 1

Fiddle

根据提供的详细信息，这是一个猜测。

此解决方案通过为这种情况推导出稍微更好的结构来避免 JOIN 问题，其中上诉和最高适用区域合并为一个 table，每种类型都有一个指示列， (1, null) 或 (null, 1) 允许在没有条件逻辑的情况下进行计数。分别计算每种类型（stype 和 atype）时，空值将被忽略。

这可以通过几种不同的方式来完成。这是一个。

SQL（对于MySQL8.0+）：

WITH area_types (atype, stype, applicable_area_id, suitno) AS (
       SELECT    1, null, applicable_area_id, suitno FROM appeal_applicable_areas
        UNION
       SELECT null,    1, applicable_area_id, suitno FROM supreme_applicable_areas
     )
SELECT applicable_areas.area
     , applicable_areas.id as id
     , count(stype) as supreme_court_cases
     , count(atype) as appeal_court_cases
  FROM applicable_areas
  JOIN area_types
    ON area_types.applicable_area_id = applicable_areas.id
  JOIN cp_cases_counsel
    ON cp_cases_counsel.suitno = area_types.suitno
 WHERE cp_cases_counsel.councel_id = 54
 GROUP BY applicable_areas.id
 ORDER BY applicable_areas.area ASC
;

并且因为我将 id 设为 applicable_areas 的 primary key，我们真的不需要 GROUP BY 条款中的 area（参见：functional dependence).我已经删除了它。

对于 8.0 之前的 MySQL：

SELECT applicable_areas.area
     , applicable_areas.id as id
     , count(stype) as supreme_court_cases
     , count(atype) as appeal_court_cases
  FROM applicable_areas
  JOIN (
           SELECT    1 AS atype, null AS stype, applicable_area_id, suitno FROM appeal_applicable_areas
            UNION
           SELECT null         ,    1         , applicable_area_id, suitno FROM supreme_applicable_areas
       ) AS area_types
    ON area_types.applicable_area_id = applicable_areas.id
  JOIN cp_cases_counsel
    ON cp_cases_counsel.suitno = area_types.suitno
 WHERE cp_cases_counsel.councel_id = 54
 GROUP BY applicable_areas.id
 ORDER BY applicable_areas.area ASC
;

给定一些随机数据的结果：

+------+----+---------------------+--------------------+
| area | id | supreme_court_cases | appeal_court_cases |
+------+----+---------------------+--------------------+
| 1001 |  1 |                   1 |                  1 |
| 1002 |  2 |                   1 |                  1 |
| 1003 |  3 |                   0 |                  1 |
| 1004 |  4 |                   0 |                  2 |
| 1005 |  5 |                   1 |                  0 |
| 1006 |  6 |                   1 |                  0 |
| 1007 |  7 |                   3 |                  0 |
+------+----+---------------------+--------------------+

设置：

CREATE TABLE applicable_areas        (id int primary key auto_increment, area int);
CREATE TABLE appeal_applicable_areas (applicable_area_id int, suitno int);
CREATE TABLE supreme_applicable_areas(applicable_area_id int, suitno int);
CREATE TABLE cp_cases_counsel        (suitno int, councel_id int);

INSERT INTO applicable_areas (area) VALUES
    ( 1001)
  , ( 1002)
  , ( 1003)
  , ( 1004)
  , ( 1005)
  , ( 1006)
  , ( 1007)
;

INSERT INTO appeal_applicable_areas (applicable_area_id, suitno) VALUES
    ( 1, 2001)
  , ( 2, 2002)
  , ( 3, 2003)
  , ( 4, 2004)
  , ( 4, 2009)
  , ( 4, 2010)
;

INSERT INTO supreme_applicable_areas (applicable_area_id, suitno) VALUES
    ( 1, 3001)
  , ( 2, 3002)
  , ( 5, 3003)
  , ( 6, 3004)
  , ( 7, 3005)
  , ( 7, 3006)
  , ( 7, 3007)
  , ( 7, 3008)
;

INSERT INTO cp_cases_counsel (suitno, councel_id) VALUES
    ( 2001,   54)
  , ( 2002,   54)
  , ( 2003,   54)
  , ( 2004,   55)
  , ( 2008,   54)
  , ( 2009,   54)
  , ( 2010,   54)
  , ( 3001,   54)
  , ( 3002,   54)
  , ( 3003,   54)
  , ( 3004,   54)
  , ( 3005,   66)
  , ( 3006,   54)
  , ( 3007,   54)
  , ( 3008,   54)
  , ( 3009,   54)
  , ( 3010,   54)
;

Mysql 返回连接表不正确值的行数

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