带大括号的SQL运算符优先级

此查询看起来不正确(缺少 ON

SELECT foo,count(*)
FROM A
JOIN (SELECT SUM(IF(bar = 2,1,0)) as bar_sum,
             SUM(IF(foo >= 1,1,0)) as foo,
             SUM(1) as sum_1
      FROM   B) as sums  -- should be `ON`
GROUP BY id, bar_sum, foo, sum_1;
        -- looks like grouping by sum_1, bar_sum is superflous

这个 GROUP BY 仅应用于外部查询。请注意,内部查询将返回单行。

SELECT SUM(IF(bar = 2,1,0)) as bar_sum,
       SUM(IF(foo >= 1,1,0)) as foo,
       SUM(1) as sum_1
FROM   B
-- single row