Question

更新：请查看第二个查询，它对此示例更具代表性

我想创建一个为每列使用不同子查询的查询。子查询将基于外部查询获得的列表。

例如：考虑tableA是一个包含30列和500万条记录的表

SELECT a, b, c,
(SELECT COUNT(a) FROM values WHERE (r = 12 AND u = 'TO') OR (r = 16 AND u IN ('TB', 'TU')) as First,
(SELECT COUNT(a) FROM values WHERE (r = 16 AND u = 'TE') OR (r = 76 AND u IN ('TE', 'TG')) as Second,
(SELECT COUNT(a) FROM values WHERE (r = 564 AND u = 'HG') OR (r = 788 AND u IN ('VD', 'BF')) as Third,
(SELECT COUNT(a) FROM values WHERE (r = 383 AND u = 'RT') OR (r = 35 AND u IN ('GR', 'EZ')) as Fourth
FROM tableA values

我知道这个查询不会执行，因为我无法调用子查询中的值，但是有一个很好的解决方案可以让这个查询快速运行吗？

在某些子查询中，我还需要加入另一个表，是否仍然可以使用值，还是我必须再次在tableA上执行子查询？

以下查询对此示例更具代表性：

SELECT col1, col2,

(SELECT COUNT(col3) FROM tableA ta
INNER JOIN tableB b ON tl.TaskId = b.col6
INNER JOIN tableC c ON b.Id = c.TaskId
WHERE c.ResultCode = 1 AND ta.col4 = a.col4 AND ta.col5 = a.col5) as Executed,

(SELECT COUNT(col3) FROM tableA ta
INNER JOIN tableB b ON tl.TaskId = b.col6
INNER JOIN tableC c ON b.Id = c.TaskId
WHERE c.ResultCode = 9 AND ta.col4 = a.col4 AND ta.col5 = a.col5) as NotExecuted

FROM tableA a
GROUP BY col1, col2, col4, col5

Answer 1

SELECT a, b, c,
       SUM(CASE WHEN a IS NOT NULL AND b=12 THEN 1 ELSE 0 END) as First,
       SUM(CASE WHEN a IS NOT NULL AND b=16 THEN 1 ELSE 0 END) as Second, 
       SUM(CASE WHEN a IS NOT NULL AND b=82 THEN 1 ELSE 0 END) as Third,
       SUM(CASE WHEN a IS NOT NULL AND b=167 THEN 1 ELSE 0 END) as Fourth
    FROM tableA        
    GROUP BY a, b, c

外部查询

1 个答案: