MySQL join multiple tables? - mysql

Question

I have 3 tables
tblMarkers
tblReviews
tblImages
I want to return ALL the records from tblMarkers and a count of all the reviews and images for each marker.
To complicate it further it should return all the markers within a radius of a known point.
so the expected result would be
MarkerID-MarkerName-ReviewCount-ImageCount
1223-SomeName-0-1
This is what I have so far and this returns a count of reviews, but I cant get the right SQL to add the count of images
SELECT
`tblMarkers`.`ID`,
`tblMarkers`.`Type`,
`tblMarkers`.`Name`,
`tblMarkers`.`Latitude`,
`tblMarkers`.`Longitude`,
(3959 * acos( cos( radians('45.1') ) * cos( radians( Latitude ) ) * cos( radians( Longitude ) - radians('6') ) + sin( radians('45.1') ) * sin( radians( Latitude ) ) ) )
AS distance,
Count(`tblReviews`.`marker_id`) As reviewCount
FROM
`tblMarkers`
LEFT JOIN `tblReviews` ON `tblMarkers`.`ID` = `tblReviews`.`marker_id`
GROUP BY
`tblMarkers`.`ID`,
`tblMarkers`.`Type`,
`tblMarkers`.`Name`,
`tblMarkers`.`Latitude`,
`tblMarkers`.`Longitude`
HAVING
`distance` < '50'
ORDER BY
distance;
The Images table structure is
ID [primaryKey] (same as tblMarkers.ID)
file
title
How do I add a count of all the images?

Answer 1

Try this:
SELECT M.ID
, M.Type
, M.Name
, M.Latitude
, M.Longitude
, (3959 * acos(cos(radians('45.1')) * cos(radians(M.Latitude )) * cos(radians(M.Longitude) - radians('6')) + sin(radians('45.1')) * sin(radians(M.Latitude )))) AS distance
, IFNULL(COUNT(DISTINCT R.review_id) , 0) AS ReviewCount
, IFNULL(COUNT(DISTINCT I.ID), 0) AS ImageCount
FROM tblMarkers AS M
LEFT JOIN tblReviews AS R ON R.marker_id = M.ID
LEFT JOIN tblImages AS I ON I.marker_id = M.ID
GROUP BY M.ID, M.Type, M.Name, M.Latitude, M.Longitude
HAVING distance < 50
ORDER BY distance
I bet you already know LEFT JOIN. So I used COUNT(DISTINCT R.review_id)) to count all distinct review id's (just make sure that review_id is unique). In case there are no corresponding review and image record for a specific marker record, I used IFNULL(XXX , 0) to display 0.
I used ALIASES to make your query clean and neat. Feel free to ask.

Answer 2

IF ID field of image table is the reference of marker table ID field then the query will be:
SELECT
`tblMarkers`.`ID`,
`tblMarkers`.`Type`,
`tblMarkers`.`Name`,
`tblMarkers`.`Latitude`,
`tblMarkers`.`Longitude`,
(3959 * acos( cos( radians('45.1') ) * cos( radians( Latitude ) ) * cos( radians( Longitude ) - radians('6') ) + sin( radians('45.1') ) * sin( radians( Latitude ) ) ) )
AS distance,
Count(`tblReviews`.`marker_id`) As reviewCount,
Count(`tblImage`.`ID`) As imageCount,
FROM
`tblMarkers`
LEFT JOIN `tblReviews` ON `tblMarkers`.`ID` = `tblReviews`.`marker_id`
LEFT JOIN `tblImage` ON `tblMarkers`.`ID` = `tblImages`.`ID`
GROUP BY
`tblMarkers`.`ID`,
`tblMarkers`.`Type`,
`tblMarkers`.`Name`,
`tblMarkers`.`Latitude`,
`tblMarkers`.`Longitude`
HAVING
`distance` < '50'
ORDER BY
distance;