Question

我有sql查询，它接受一个Key并输出一组记录{S}。

如何创建一个SQLite递归查询，该查询接受一组N个键，返回所有集合的交集{{S1}，{S2}，{S3}}

无需生成复制/粘贴的SQL语句。

我举一个简单的例子。所以这是交叉的明显答案。

SELECT record from RecordSet where key = 'KEY1'
INTERSECT
SELECT record from RecordSet where key = 'KEY2'

我不想做的是像这样复制和粘贴：

SELECT record from RecordSet where key = 'KEY1'
INTERSECT
SELECT record from RecordSet where key = 'KEY2'
INTERSECT
SELECT record from RecordSet where key = 'KEYN'

而是使用这里看到的递归查询功能： WITH RECURSIVE Example Here Under Recurisve Query Example

我可以传递所有密钥

SELECT key from KEYS where key in (KEY1, KEY2, KEY3, ..., KEYN)
To this recursive query.

Answer 1

尝试这样的查询：

WITH abc AS(
  SELECT Kej, val,
         (SELECT count(DISTINCT kej) FROM mytable b WHERE b.kej < a.kej) As cnt
  FROM mytable a
),
bcd AS (
   SELECT * FROM abc WHERE cnt = (SELECT max(cnt) FROM abc)
   UNION ALL
   SELECT a.* FROM abc a
   JOIN bcd b ON a.cnt = b.cnt - 1 
              AND a.val = b.val
)
SELECT val FROM bcd
WHERE cnt = 0

演示：SQL Fiddle 上述查询的工作原理是只检查了一个列以进行交集如果您的表有N个列（val1，val2，... valN），则连接必须包含所有这些列：

   JOIN bcd b ON a.cnt = b.cnt - 1 
              AND a.val1 = b.val1
              AND a.val2 = b.val2
              .....
              AND a.valN = b.valN

SQLite递归交集

1 个答案: