根据第三列的值，我如何在一列中进行聚合？

Question

我有以下的表有三列：

id | type | value 
-----+------+------- 
foo | bar | 123 
foo | bar | 456 
foo | biz | 789 
foo | biz | 987 
baz | bar | 555 
quz | biz | 777 

我试图在给定type聚集value，返回这样的结果：

id |  bar  | biz 
-----+---------------+----------- 
foo | {123,456}  | {789,987} 
baz | {555}   | {} 
quz | {}   | {777} 

我到目前为止已经试过自动加入表格两次（使用LEFT JOIN来计算空列），然后执行DISTINCT以在汇总之前删除重复项。有没有更好的办法？

目前查询：

SELECT 
    test.id, 
    ARRAY_REMOVE(ARRAY_AGG(DISTINCT(t1.value)), NULL) AS bar, 
    ARRAY_REMOVE(ARRAY_AGG(DISTINCT(t2.value)), NULL) AS biz 
FROM test 
LEFT JOIN test t1 ON test.id = t1.id AND t1.type = 'bar' 
LEFT JOIN test t2 ON test.id = t2.id AND t2.type = 'biz' 
GROUP BY test.id; 

Answer 1

尝试：

SELECT id, 
     ARRAY_REMOVE(Array_agg(bar), NULL) as bbar, 
     ARRAY_REMOVE(Array_agg(biz), NULL) as bbiz 
FROM (
    SELECT id, 
    CASE WHEN type = 'bar' THEN value ELSE NULL END AS bar, 
    CASE WHEN type = 'biz' THEN value ELSE NULL END AS biz 
    FROM test 
) x 
GROUP BY id