有條件的聚合與GROUP By子句

Question

我想用HiveQL來做到這一點，但我不知道如何在SQL中做到這一點。表結構如下：

 
id1 id2 category 
123 abc 1 
123 def 1 
123 def 2 
456 abc 1 
123 abc 1 
123 abc 2 
... 

我想寫輸出的查詢：

 
key   count  category1count category2count 
123-abc  3    2     1 
123-def  2    1     1 
456-abc  1    1     0 

到目前爲止，我有這樣的：

SELECT concat(concat(id1,'-'), id2), count(*) , 
count(SELECT * WHERE buyingcategory = 1 ???) , 
count(SELECT * WHERE buyingcategory = 2 ???) 
FROM table 
GROUP BY concat(concat(id1,'-'), id2) 

Answer 1

試試這個

SELECT concat(id1,'-', id2) `key`, count(*) , 
sum(case when category = 1 then 1 else 0 end) category1count , 
sum(case when category = 2 then 1 else 0 end) category2count 
FROM table1 
GROUP BY concat(id1,'-', id2) 

DEMO HERE