[英]SQL aggregate group by columns
我有一張桌子,看起來像這樣:
price is_a is_b is_c ...
300 1 0 1 ...
500 0 1 0 ...
200 1 1 1 ...
400 0 1 1 ...
我現在想為每個“ is_”屬性選擇平均價格:
avg(price) is_a is_b is_c
250 1 0 0
367 0 1 0
300 0 0 1
我當前正在使用以下查詢,該查詢顯然返回所有屬性的所有可能組合(在這種情況下,與上面的表完全相同):
SELECT avg(price), is_a, is_b, is_c, ... FROM table GROUP BY is_a, is_b, is_c, ...
您將需要使用聯合。 但是,您將兩次計數某些事件:
SELECT avg(price), 1, 0, 0 ... FROM table WHERE is_a = 1
UNION
SELECT avg(price), 0, 1, 0 ... FROM table WHERE is_b = 1
UNION
SELECT avg(price), 0, 0, 1 ... FROM table WHERE is_c = 1
就像我說過的,如果存在與is_a 和 is_b匹配的記錄,則它們的價格將計入第一列和第二列。
Use CTE to get your result :
CREATE TABLE #table(price INT,is_a INT,is_b INT,is_c INT)
INSERT INTO #table(price ,is_a ,is_b ,is_c)
SELECT 300,1,0,1 UNION ALL
SELECT 500,0,1,0 UNION ALL
SELECT 200,1,1,1 UNION ALL
SELECT 400,0,1,1
;WITH _CTEAvg ( Avgprice , is_a , is_b , is_c ) AS
(
SELECT AVG(price) , 1 , 0 , 0
FROM #table
WHERE is_a = 1
GROUP BY is_a
UNION ALL
SELECT AVG(price) , 0 , 1 , 0
FROM #table
WHERE is_b = 1
GROUP BY is_b
UNION ALL
SELECT AVG(price) , 0 , 0 , 1
FROM #table
WHERE is_c = 1
GROUP BY is_c
)
SELECT * FROM _CTEAvg
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