Question

I am trying to choose the row where

1)list.ispublic = 1
2)userlist.userid='aaa' AND userlist.listid=list.listid

I need 1)+2)

There is a row already but this statement can not get that row, is there any problem?

List table:

ListID  ListName    Creator IsRemindSub IsRemindUnSub   IsPublic    CreateDate  LastModified    Reminder
1       test2       aaa     0           0               1           2012-03-09  NULL            NULL

user_list table (No row):

UserID ListID UserRights

My test version

SELECT * 
FROM list l 
INNER JOIN user_list ul ON ul.ListID = l.ListID 
WHERE l.IsPublic = 1 AND ul.UserID = '09185346d'

This is the Result when there are two list in user_list has aaa , and one list is public in list, so will this cause double retrieve of that one public list in list if i get it in php ?

ListID    ListName    Creator    IsRemindSub    IsRemindUnSub    IsPublic    CreateDate    LastModified    Reminder    UserID    ListID    UserRights
1         test2       aaa        0              0                1           2012-03-09    NULL                        aaa       1         read
2         t2          aaa        0              0                1           2012-03-09    NULL                        aaa       2         read

Answer 1

First, try to only SELECT the fields you actually need. Second, write your JOINS explicitly – it helps readability. For example:

SELECT l.*, ul.*
FROM list l
INNER JOIN user_list ul ON ul.ListID = l.ListID
WHERE l.IsPublic = 1
  AND ul.UserID = 'aaa'

Incidentally, if you have no data in your user_list table, then you have no way to meet the requirements you have set. If as you put it “userlist.listid=list.listid” is necessary and the user_list table is empty, you will always get zero rows returned.

Edit: And no, it won’t cause rows to be retrieved double. Whatever results you get with your SQL query will be the same results you get in a PHP script – the mechanism for retrieving the data is the same.