如何在MySQL中使用帶有條件的案例

Question

使用mysql查詢如何使用條件為case （ manager_id=2 ）的情況。

我有三個表列

user
 - id
 - name
 - dept
 - manager_id
itemone
 - id
 - detail
 - status
 - amount
 - created_by
itemtwo
 - id
 - detail
 - status
 - amount
 - created_by

根據status欄可以找到草稿，待審核，已批准和已拒絕 。

當我的manager_id為2 ，如果未顯示為0.00，則計算pending總數； 如何為此編寫查詢？

樣本選擇查詢：

SELECT t1.name, t1.dept, t1.manager_id, t2.draft_total, t2.pending_total, t2.approved_total, t2.rejected_total FROM user t1, 
(
    SELECT uat.created_by, SUM(uat.amount) AS total, SUM(uat.draft) AS draft_total, SUM(uat.pending) AS pending_total, SUM(uat.approved) AS approved_total, SUM(uat.rejected) AS rejected_total FROM 
    (
        SELECT id, detail, status, amount, CASE status WHEN 1 THEN amount ELSE 0 END AS draft, CASE status WHEN 2 THEN amount ELSE 0 END AS pending, CASE status WHEN 3 THEN amount ELSE 0 END AS approved, CASE status WHEN 4 THEN amount ELSE 0 END AS rejected,created_by FROM itemone UNION ALL SELECT id, detail, status, amount, CASE status WHEN 1 THEN amount ELSE 0 END AS draft, CASE status WHEN 2 THEN amount ELSE 0 END AS pending, CASE status WHEN 3 THEN amount ELSE 0 END AS approved, CASE status WHEN 4 THEN amount ELSE 0 END AS rejected,created_by FROM itemtwo
    ) 
    uat GROUP BY uat.created_by
) t2 WHERE t1.id=t2.created_by ORDER BY name ASC;

在SQLFiddle中查找表架構

獲得跟蹤結果

 name       | dept  | manager_id    | draft_total   | pending_total | approved_total    | rejected_total
user four   | Y     | 2             | 79.75         | 54.10         | 90.30             | 100.20  
user one    | X     | 1             | 79.75         | 54.10         | 90.30             | 100.20
user two    | X     | 1             | 84.25         | 0.00          | 0.00              | 0.00

預期輸出：如果Manager id為2，則結果應為

name        | dept  | manager_id    | draft_total   | pending_total | approved_total    | rejected_total
user four   | Y     | 2             | 79.75         | 54.10         | 90.30             | 100.20  
user one    | X     | 1             | 79.75         | 0.00          | 90.30             | 100.20
user two    | X     | 1             | 84.25         | 0.00          | 0.00              | 0.00

Answer 1

試試這個：

SELECT t1.name, t1.dept, t1.manager_id,
sum(case when t2.status=1 then t2.amount else 0 end) AS draft_total, 
sum(case when t2.status=2 and t1.manager_id=2  then t2.amount else 0 end) AS pending_total, 
sum(case when t2.status=2 then t2.amount else 0 end) AS approved_total, 
sum(case when t2.status=4 then t2.amount else 0 end) AS rejected_total
FROM user t1
inner join (
  select * from itemone
  union all 
  select * from itemtwo
) t2 on t1.id=t2.created_by 
group by t1.id
ORDER BY t1.name ASC

Answer 2

試試這個

SELECT CASE user.manager_id何時2 THEN SUM（pending）ELSE 0 END asending_total FROM ... WHERE ...