[英]Multiple Left Join on same table
我有兩張桌子。 1st table => member {member_id,name,active} 2nd table => savings {savings_id,member_id,month,year,amount,type,paid}
會員表
+-----------+--------+--------+
| member_id | name | active |
+-----------+--------+--------+
| 105 | Andri | 1 |
| 106 | Steve | 1 |
| 110 | Soraya | 1 |
| 111 | Eva | 1 |
| 112 | Sonia | 1 |
+-----------+--------+--------+
儲蓄表
+------------+-----------+-------+------+--------+------+------+
| savings_id | member_id | month | year | amount | type | paid |
+------------+-----------+-------+------+--------+------+------+
| 1 | 120 | NULL | NULL | 150000 | 1 | 1 |
| 14 | 105 | 7 | 2014 | 80000 | 2 | 1 |
| 15 | 105 | 7 | 2014 | 25000 | 3 | 1 |
| 16 | 105 | 7 | 2014 | 60000 | 4 | 1 |
| 17 | 105 | 7 | 2014 | 100000 | 5 | 1 |
| 18 | 106 | 7 | 2014 | 80000 | 2 | 1 |
| 19 | 106 | 7 | 2014 | 25000 | 3 | 1 |
| 20 | 106 | 7 | 2014 | 60000 | 4 | 1 |
| 21 | 106 | 7 | 2014 | 100000 | 5 | 1 |
| 31 | 110 | 7 | 2014 | 25000 | 3 | 1 |
| 32 | 110 | 7 | 2014 | 60000 | 4 | 1 |
| 33 | 110 | 7 | 2014 | 100000 | 5 | 1 |
| 34 | 111 | 7 | 2014 | 80000 | 2 | 1 |
| 35 | 111 | 7 | 2014 | 25000 | 3 | 1 |
| 36 | 111 | 7 | 2014 | 60000 | 4 | 1 |
| 37 | 111 | 7 | 2014 | 100000 | 5 | 1 |
| 38 | 112 | 7 | 2014 | 80000 | 2 | 1 |
| 39 | 112 | 7 | 2014 | 25000 | 3 | 1 |
| 40 | 112 | 7 | 2014 | 60000 | 4 | 1 |
| 41 | 112 | 7 | 2014 | 100000 | 5 | 1 |
| 85 | 105 | 7 | 2015 | 80000 | 2 | 1 |
| 86 | 105 | 7 | 2015 | 25000 | 3 | 1 |
| 87 | 105 | 7 | 2015 | 60000 | 4 | 1 |
| 88 | 105 | 7 | 2015 | 100000 | 5 | 1 |
| 89 | 106 | 7 | 2015 | 80000 | 2 | |
| 90 | 106 | 7 | 2015 | 25000 | 3 | |
| 91 | 106 | 7 | 2015 | 60000 | 4 | |
| 92 | 106 | 7 | 2015 | 100000 | 5 | |
| 101 | 110 | 7 | 2015 | 80000 | 2 | |
| 102 | 110 | 7 | 2015 | 25000 | 3 | |
| 103 | 110 | 7 | 2015 | 60000 | 4 | |
| 104 | 110 | 7 | 2015 | 100000 | 5 | |
| 105 | 111 | 7 | 2015 | 80000 | 2 | 1 |
| 106 | 111 | 7 | 2015 | 25000 | 3 | 1 |
| 107 | 111 | 7 | 2015 | 60000 | 4 | 1 |
| 108 | 111 | 7 | 2015 | 100000 | 5 | 1 |
| 109 | 112 | 7 | 2015 | 80000 | 2 | |
| 110 | 112 | 7 | 2015 | 25000 | 3 | |
| 111 | 112 | 7 | 2015 | 60000 | 4 | |
| 144 | 110 | 7 | 2014 | 50000 | 1 | 1 |
+------------+-----------+-------+------+--------+------+------+
當會員節省開支時,他們可以選擇5種類型的儲蓄,我想做的是列出會員名單和所有儲蓄。
這是mysql查詢
SELECT m.member_id, name,
SUM(s1.amount) as savings1,
SUM(s2.amount) as savings2,
SUM(s3.amount) as savings3,
SUM(s4.amount) as savings4,
SUM(s5.amount) as savings5
FROM members m
LEFT JOIN savings s1 ON s1.member_id = m.member_id AND s1.type = 1 AND s1.paid = 1
LEFT JOIN savings s2 ON s2.member_id = m.member_id AND s2.type = 2 AND s2.paid = 1
LEFT JOIN savings s3 ON s3.member_id = m.member_id AND s3.type = 3 AND s3.paid = 1
LEFT JOIN savings s4 ON s4.member_id = m.member_id AND s4.type = 4 AND s4.paid = 1
LEFT JOIN savings s5 ON s5.member_id = m.member_id AND s5.type = 5 AND s5.paid = 1
WHERE
active = 1
GROUP BY m.member_id
這是輸出
+-----------+--------+----------+----------+----------+----------+----------+
| member_id | name | savings1 | savings2 | savings3 | savings4 | savings5 |
+-----------+--------+----------+----------+----------+----------+----------+
| 105 | Andri | NULL | 1280000 | 400000 | 960000 | 1600000 |
| 106 | Steve | NULL | 80000 | 25000 | 60000 | 100000 |
| 110 | Soraya | 50000 | NULL | 25000 | 60000 | 100000 |
| 111 | Eva | NULL | 1280000 | 400000 | 960000 | 1600000 |
| 112 | Sonia | NULL | 80000 | 25000 | 60000 | 100000 |
+-----------+--------+----------+----------+----------+----------+----------+
如您所見,計算結果不正確,例如成員105的Saving2應為160K。 任何建議應該是這種情況的查詢。
問題是你在求和之前正在形成完整的連接產品。 因此,如果您的多個savings
表中有多行,則最終會出現重復。 如果您在沒有求和的情況下執行連接 ,您可以清楚地看到發生了什么。 有兩種方法可以解決這個問題。
在派生表中執行所有求和:
SELECT m.member_id, name, s1.amount as savings1, s2.amount as savings2, ... FROM members m LEFT JOIN ( select SUM(amount) as amount, member_id from savings where type = 1 and paid = 1 group by member_id ) s1 ON s1.member_id = m.member_id LEFT JOIN ( select SUM(amount) as amount, member_id from savings where type = 2 and paid = 1 group by member_id ) s2 ON s2.member_id = m.member_id ... WHERE active = 1 GROUP BY m.member_id
加入一次並使用條件總和:
SELECT m.member_id, name, SUM(CASE WHEN s.type = 1 then s.amount ELSE NULL END) as savings1, SUM(CASE WHEN s.type = 2 then s.amount ELSE NULL END) as savings2, ... LEFT JOIN savings s s2 ON s.member_id = m.member_id AND s.paid = 1 WHERE active = 1 GROUP BY m.member_id
您可能不需要多個左連接,可以完成
SELECT
m.member_id,
m.name,
SUM(case when s.type= 1 then s.amount end) as savings1,
SUM(case when s.type= 2 then s.amount end) as savings2,
SUM(case when s.type= 3 then s.amount end) as savings3,
SUM(case when s.type= 4 then s.amount end) as savings4,
SUM(case when s.type= 5 then s.amount end) as savings5
FROM savings s
join members m on m.member_id = s.member_id
WHERE
m.active = 1
GROUP BY m.member_id
這應該工作
SELECT m.member_id, name,
sum((case when s1.type=1 then s1.amount end)) as savings1,
sum((case when s1.type=2 then s1.amount end)) as savings2,
sum((case when s1.type=3 then s1.amount end)) as savings3,
sum((case when s1.type=4 then s1.amount end)) as savings4,
sum((case when s1.type=5 then s1.amount end)) as savings5
FROM members m
LEFT JOIN savings s1 ON s1.member_id = m.member_id
WHERE active = 1 and s1.paid=1
GROUP BY m.member_id
似乎加入有問題..你可以去上面的答案所有都是很好的選擇..
你也可以使用Pivot Query
SELECT m.member_id,s1.type,
SUM(s1.amount) as savings
FROM members m
LEFT JOIN savings s1 ON s1.member_id = m.member_id AND s1.paid = 1
WHERE active = 1
GROUP BY m.member_id ,s1.type
//轉到這里
然后嘗試透視dude ..那也很好......
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