我有两个 SQL 查询来计算不同 id1 值中 id2 值之间的共现。示例表看起来像
id1 | id2
101 | 1
101 | 2
101 | 3
102 | 2
102 | 3
102 | 4
103 | 15
103 | 3
103 | 4
所需的输出是:
A B Count
1 2 1
1 3 2
2 3 4
1 4 2
2 4 3
3 4 4
1 15 1
2 15 2
3 15 2
4 15 1
两种解决方案都粘贴在下面。
-- Solution 1
SELECT bar.id2 AS A, foo.id2 AS B, COUNT(*) AS Count
FROM
(SELECT * FROM TestTab) AS bar,
(SELECT * FROM TestTab) AS foo
WHERE bar.id1 <> foo.id1
AND bar.id2 < foo.id2
GROUP BY bar.id2, foo.id2
-- Solution 2
SELECT bar.id2 AS A, foo.id2 AS B, COUNT(*) AS Count
FROM TestTab AS bar
JOIN TestTab AS foo
ON bar.id1 <> foo.id1
WHERE bar.id2 < foo.id2
GROUP BY bar.id2, foo.id2
这两个查询都适用于小表(即 100 - 1000 行),但我需要查询更大的表(例如 100.000 行)。我想知道如何加快查询速度并提高性能。在此先感谢您的任何指点。
- Create table TestTab and insert dummy data
CREATE TABLE TestTab
INSERT INTO TestTab VALUES
(101,1),
(101,2),
(101,3),
(102,2),
(102,3),
(102,4),
(103,15),
(103,3),
(103,4)