Question

我有一个问题，我需要多次在同一个表上加入并计算JOINS。

这是数据库设置（SQL Fiddle ）：

CREATE TABLE state
(
  [t_id] int,
  [true_id] int,
  [false_id] int,
  [msg] varchar(32) 
);

INSERT INTO state
  (t_id, true_id, false_id, msg)
VALUES
  (5, 6, 7, 'CASE_1'),
  (10, 11, 12, 'CASE_2'),
  (20, 21, 22, 'CASE_N'),
  (30, 31, 32, 'FOOOO');

CREATE TABLE step
(
      [id] int,
      [f_id] int,
      [state_type] int,
      [state_value] int
);

INSERT INTO step
    (id,f_id,state_type, state_value)
VALUES
    (1, 5, 5, 7),
    (2, 5, 5, 7),
    (3, 5, 5, 6),

    (4, 5, 10, 12),
    (5, 5, 10, 12),
    (6, 5, 10, 11),

    (7, 6, 10, 12),
    (8, 6, 10, 12),

    (9, 7, 20, 21),
    (10, 7, 20, 21),

    (11, 7, 30, 32),
    (12,7, 30, 31);

这是我当前的查询：

SELECT state.msg, 
  COUNT(state_true.true_id) AS Trues,
  COUNT(state_false.false_id) AS Falses
FROM state
  INNER JOIN step ON state.t_id = step.state_type
  LEFT OUTER JOIN state AS state_true ON step.state_value = state_true.true_id
  LEFT OUTER JOIN state AS state_false ON step.state_value = state_false.false_id
GROUP BY state.msg, step.f_id

这就是我得到的：

msg     Trues   Falses
CASE_1  1       2
CASE_2  1       2
CASE_2  0       2
CASE_N  2       0
FOOOO   1       1

这就是我需要的：

msg     Trues   Falses
CASE_1  1       0
CASE_2  1       1
CASE_N  1       0
FOOOO   1       0

有关说明：

我需要计算每个 state_type和f_id 组合有多少真实和失败。

f_id = 5共有6个条目 - ＆gt; (1,2,3,4,5,6)。如果存在具有相同(f_id,state_type)组合的条目，则只应计算最后一个条目。因此，对于f_id 5，条目1,2,4,5不应计入计数，因为它们被3和6 覆盖。

因此，在处理完前6个条目后，应该CASE_1 true => 1 false => 0和CASE_2 true => 1 false => 0

__编辑__

 TABLE step:

(1, 5, 5, 7),  -- do not count
(2, 5, 5, 7),  -- do not count
(3, 5, 5, 6),  -- this is the last entry with 
               -- (f_id,state_type) => (5,5) combination. 
               -- it overwrites the 2 previous ones => count CASE_1 true

(4, 5, 10, 12), -- do not count
(5, 5, 10, 12), -- do not count
(6, 5, 10, 11), -- count CASE_2 true

(7, 6, 10, 12), -- do not count
(8, 6, 10, 12), -- count CASE_2 false

(9, 7, 20, 21),  -- do not count
(10, 7, 20, 21), -- count CASE_N false

(11, 7, 30, 32), -- do not count
(12,7, 30, 31);  -- count FOOOO true

Answer 1

我不确定我是否完全明白你的意图，但也许下面的查询可能是你想要的？鉴于您的样本数据，它似乎产生了正确的输出。

SELECT state.msg, 
  SUM(CASE WHEN true_id  = state_value THEN 1 ELSE 0 END) AS Trues,
  SUM(CASE WHEN false_id = state_value THEN 1 ELSE 0 END) AS Falses
FROM state
JOIN step ON state.t_id = step.state_type
JOIN (SELECT MAX(id) mid FROM step GROUP BY f_id, state_type) a ON a.mid = step.id
GROUP BY state.msg;

请试一试。如果我误解了，我会删除答案。

SQL计数由多列连接

1 个答案: