SELECT DISTINCT Customers.customer_id, Customers.first_name

FROM Customers

INNER JOIN Orders

ON Customers.customer_id = Orders.customer_id

ORDER BY Customers.customer_id;

SELECT * 

FROM

( SELECT ... FROM ... ) q1

​

INNER JOIN

​

( SELECT ... FROM ... ) q2

​

ON q1.colname = q2.colname

SELECT

  s.studentid,

  s.studentname,

  s.gender,

  GROUP_CONCAT(DISTINCT ss.subjectName) AS subjectNames,

  (

    SELECT GROUP_CONCAT(DISTINCT name)

    FROM games

    WHERE FIND_IN_SET(games.id, s.fkgameid)

  ) AS game_names,

  GROUP_CONCAT(DISTINCT ss.marks) AS marks,

  GROUP_CONCAT(DISTINCT sc.city) AS cities,

  GROUP_CONCAT(DISTINCT sc.province) AS provinces,

  s.image

FROM student s

LEFT JOIN studentsubject ss ON s.studentid = ss.fkstudentid

LEFT JOIN studentcity sc ON s.studentid = sc.fkstudentid

WHERE s.studentid = '1'

GROUP BY s.studentid, s.studentname, s.gender, s.image, s.fkgameid;

​

    (select coalesce((select name from object_value where object_id = addtl_type.id 

    and object_type_id = @object_type_des_UDF

    and language_id = @language_id),addtl_type.name) from addtl_type

    where id = (select n_value from pr_addtl_data where pr_id = PR.ID and 

    data_field_id = (select id from data_fields where name = 'Category'))) as 'Category',