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[英]Return all possible combinations of values within a single column in MySQL
[英]Return all possible combinations of values within a single column in SQL
如何从数据库'x'的同一列中返回所有可能值组合的列表? 例如,我有:
col 1,
1
2
3
4
我想返回所有可能组合的列表,例如
1,2
1,3
1,4
2,3,
2,4
3,4
....
您没有说过您正在使用哪种RDBMS,或者您是否想要将组合限制为该组的2个元素。
以下是使用分层查询的Oracle答案:
Oracle 11g R2架构设置 :
CREATE TABLE TEST ( COL ) AS
SELECT LEVEL FROM DUAL CONNECT BY LEVEL < 5;
查询1 :
SELECT SUBSTR(SYS_CONNECT_BY_PATH(COL, ','), 2) AS combination
FROM TEST
CONNECT BY PRIOR COL < COL
结果 :
| COMBINATION |
|-------------|
| 1 |
| 1,2 |
| 1,2,3 |
| 1,2,3,4 |
| 1,2,4 |
| 1,3 |
| 1,3,4 |
| 1,4 |
| 2 |
| 2,3 |
| 2,3,4 |
| 2,4 |
| 3 |
| 3,4 |
| 4 |
查询2 :
SELECT SUBSTR(SYS_CONNECT_BY_PATH(COL, ','), 2) AS combination
FROM TEST
WHERE LEVEL = 2
CONNECT BY PRIOR COL < COL AND LEVEL <= 2
结果 :
| COMBINATION |
|-------------|
| 1,2 |
| 1,3 |
| 1,4 |
| 2,3 |
| 2,4 |
| 3,4 |
和使用递归CTE的SQL Server版本:
MS SQL Server 2014架构设置 :
CREATE TABLE TEST ( COL INT );
INSERT INTO TEST
SELECT 1
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4;
查询1 :
WITH cte ( combination, curr ) AS (
SELECT CAST( t.COL AS VARCHAR(80) ),
t.COL
FROM TEST t
UNION ALL
SELECT CAST( c.combination + ',' + CAST( t.col AS VARCHAR(1) ) AS VARCHAR(80) ),
t.COL
FROM TEST t
INNER JOIN
cte c
ON ( c.curr < t.COL )
)
SELECT combination FROM cte
结果 :
| combination |
|-------------|
| 1 |
| 2 |
| 3 |
| 4 |
| 3,4 |
| 2,3 |
| 2,4 |
| 2,3,4 |
| 1,2 |
| 1,3 |
| 1,4 |
| 1,3,4 |
| 1,2,3 |
| 1,2,4 |
| 1,2,3,4 |
select concat(t1.id, ",", t2.id) from t t1 join t t2 on t1.id < t2.id;
可以在此处找到SQL小提琴示例。
concat(t1.id, ",", t2.id)
-------------------------
1,2
1,3
1,4
2,4
2,3
3,4
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