Does anyone know how to create a table with m columns from table of n rows where the values in columns of each row represent a different combination or permutation of values from the original table?
有没有人知道如何从n行表中创建一个包含m列的表，其中每行的列中的值表示原始表中值的不同组合或排列？
For example the original table has 1 column (number_value) with 3 (n=3) rows:
例如，原始表有1列（number_value），其中3（n = 3）行：
1
2
3
The table which contains combinations (the order doesn't matter) of two values (m = 2) would be the following:
包含两个值（m = 2）的组合（顺序无关紧要）的表格如下：
number1, number2
1,2
1,3
2,3
and the table of permutations would be the following:
排列表如下：
number1, number2
1, 2
2, 1
1, 3
3, 1
2, 3
3, 2
The order of rows doesn't matter.
行的顺序无关紧要。
Thank you in advance!
先谢谢你！
1 个解决方案
#1
29
Combinations:
组合：
SELECT T1.x, T2.x
FROM your_table T1
JOIN your_table T2
ON T1.x < T2.x
Permutations:
排列：
SELECT T1.x, T2.x
FROM your_table T1
JOIN your_table T2
ON T1.x != T2.x
I am assuming that the values in the original table are unique.
我假设原始表中的值是唯一的。
To generalize for larger values of m you need to add more joins.
要概括m的较大值，您需要添加更多连接。
#1
29
Combinations:
组合：
SELECT T1.x, T2.x
FROM your_table T1
JOIN your_table T2
ON T1.x < T2.x
Permutations:
排列：
SELECT T1.x, T2.x
FROM your_table T1
JOIN your_table T2
ON T1.x != T2.x
I am assuming that the values in the original table are unique.
我假设原始表中的值是唯一的。
To generalize for larger values of m you need to add more joins.
要概括m的较大值，您需要添加更多连接。