如下所示的表
-----------------------
num1 num2
a b
a c
a b
b a
c a
a c
-----------------------
将(a,b)和(b,a)视作相同
统计出例如(a,b)或者(b,a)出现的频率?
比如上表中(a,b)出现2次,(b,a)出现1次,即(a,b)或者(b,a)次数为3次请教了
-----------------------
num1 num2
a b
a c
a b
b a
c a
a c
-----------------------
将(a,b)和(b,a)视作相同
统计出例如(a,b)或者(b,a)出现的频率?
比如上表中(a,b)出现2次,(b,a)出现1次,即(a,b)或者(b,a)次数为3次请教了
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+------+------+
| num1 | num2 |
+------+------+
| a | b |
| a | c |
| a | b |
| b | a |
| c | a |
| a | c |
+------+------+
6 rows in set (0.00 sec)mysql> select t.num1,t.num2,count(*)
-> from (
-> select num1,num2 from tx
-> union all
-> select num2,num1 from tx
-> ) t
-> group by t.num1,t.num2;
+------+------+----------+
| num1 | num2 | count(*) |
+------+------+----------+
| a | b | 3 |
| a | c | 3 |
| b | a | 3 |
| c | a | 3 |
+------+------+----------+
4 rows in set (0.00 sec)mysql>
-> from (
-> select num1,num2 from tx
-> union all
-> select num2,num1 from tx
-> ) t
-> where t.num1<t.num2
-> group by t.num1,t.num2;
+------+------+----------+
| num1 | num2 | count(*) |
+------+------+----------+
| a | b | 3 |
| a | c | 3 |
+------+------+----------+
2 rows in set (0.00 sec)mysql>
http://topic.csdn.net/u/20090501/15/7548d251-aec2-4975-a9bf-ca09a5551ba5.html
初次提问,还不晓得要结贴
再请教一下
还是上表
num1 num2
a b
a b
a c
c a如何选出(a,c)(c,a)这一类有交叉的
数据