用一条语句从一个表PATHWAY中选出 PATH_ID 分解开来就是
select PATH_ID from pathway where content = 'a'
select PATH_ID from pathway where content = 'b'
找出相同的所有PATH_ID。
select PATH_ID from pathway where content = 'a'
select PATH_ID from pathway where content = 'b'
找出相同的所有PATH_ID。
+------+
| p |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
表中有PATH_ID(不是主键) 和CONTENT两列要求找出CONTENT = A 和 CONTENT = B 且PATH_ID相同的所有的PATH_ID
FROM pathway p1,
pathway p2
WHERE p1.path_id = p2.path_id
AND p1.content = 'a'
AND p2.content = 'a'
where p1.PATH_ID=p2.PATH_ID
and p1.CONTENT='".$content_get1."'
and p2.CONTENT='".$content_get2."';";为什么我执行的时候还是有问题Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\pwps\from_to.php on line 12
路径共有条
Warning: mysql_fetch_assoc() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\pwps\from_to.php on line 14
FROM pathway p1,
pathway p2
WHERE p1.path_id = p2.path_id
AND p1.content = 'a'
AND p2.content = 'b';
from pathway a inn join pathway b on a.PATH_ID=b.PATH_ID
where a.CONTENT = 'A' and b.CONTENT = 'B'