using where and inner join in mysql

Question

I have three tables.

locations

ID   | NAME | TYPE |
1    | add1 | stat |
2    | add2 | coun | 
3    | add3 | coun |
4    | add4 | co         


        

Answer 1

You can use as many joins as you want, however, the more you use the more it will impact performance

Answer 2

    SELECT `locations`.`name`
      FROM `locations`
INNER JOIN `school_locations`
        ON `locations`.`id` = `school_locations`.`location_id`
INNER JOIN `schools`
        ON `school_locations`.`school_id` = `schools_id`
     WHERE `type` = 'coun';

the WHERE clause has to be at the end of the statement

Answer 3

Try this:

SELECT Locations.Name, Schools.Name
FROM Locations
INNER JOIN School_Locations ON School_Locations.Locations_Id = Locations.Id
INNER JOIN Schools ON School.Id = Schools_Locations.School_Id
WHERE Locations.Type = "coun"

You can join Locations to School_Locations and then School_Locations to School. This forms a set of all related Locations and Schools, which you can then widdle down using the WHERE clause to those whose Location is of type "coun."

Answer 4

Try this :

SELECT
    (
      SELECT
          `NAME`
      FROM
          locations
      WHERE
          ID = school_locations.LOCATION_ID
    ) as `NAME`
FROM
     school_locations
WHERE
     (
      SELECT
          `TYPE`
      FROM
          locations
      WHERE
          ID = school_locations.LOCATION_ID
     ) = 'coun';