MySQL查询没有选择不同

Question

I have a table like this :

Test_ID   Question_ID    User_ID
---------------------------------
 15           1            1
 15           2            1 
 16           1            2 

And im trying to go through the table and print out something like this for each user. :

Test id : # Number of questions : #

Im using this which I can only get to print out the test id.

 $result = mysqli_query($conn, "SELECT DISTINCT(Test_ID) AS Tcode, COUNT(Question_ID) AS Qcount,User_ID FROM user_answers WHERE User_ID = 1");

   while ($data = mysqli_fetch_array($result)) {

      echo ''.$data['Tcode'].'';
      echo ''.$data['Qcount'].'';


    }

Answer 1

use group by for aggregate function (and for this you don0t need distinct )

"SELECT Test_ID  AS Tcode, COUNT(*) AS Qcount, User_ID
      FROM user_answers
      WHERE User_ID = 1  group by Tcode, User_ID ")