Question

I have two tables –

tbl_business
------------------------
| id | name | lat |long|
|----|------|-----|----|
|  1 | aaaa |12.45|6.88|
|----|------|-----|----|
|  2 | bbbb |12.34|6.45|
|----|------|-----|----|
|  3 | cccc |12.12|6.50|
|----|------|-----|----|

and

tbl_deals
-------------------
| id | deal | bid |
|----|------|-----|
|  1 | xxxx |  1  |
|----|------|-----|
|  2 | yyyy |  1  |
|----|------|-----|
|  3 | zzzz |  2  |
|----|------|-----|

Now I want to find all the businesses that are within 1km of 12.44, 6.66, along with the deals count. E.g.

| bid |dcount|
|-----|------|
|  1  |   2  |
|-----|------|
|  2  |   1  |
|-----|------|
|  3  |   0  |
|-----|------|

I’m using this query right now –

SELECT bid, COUNT( id ) as count
FROM  `tbl_deals` 
WHERE bid
IN (
    SELECT id
    FROM tbl_business
    WHERE ( 6371 * ACOS( COS( RADIANS( 12.44 ) ) * COS( RADIANS( lat ) ) * COS( RADIANS( long ) - RADIANS( 6.66 ) ) + SIN( RADIANS( 12.44 ) ) * SIN( RADIANS( lat ) ) ) ) < 1
    )
GROUP BY bid
ORDER BY count DESC

I found the formula here. But this doesn’t show count = 0 for bid 3. I’m guessing I have to use Left join for this, but cannot figure out how.

Answer 1

Yes, you have to write an outer join, a business LEFT JOIN deals:

SELECT 
      b.id
    , COUNT( d.bid ) AS dcount
FROM  
      tbl_business AS b
  LEFT JOIN
      tbl_deals AS d 
    ON 
      d.bid = b.id
WHERE 
      ( 6371 * ACOS( COS( RADIANS( 12.44 ) ) 
                   * COS( RADIANS( lat ) ) 
                   * COS( RADIANS( long ) - RADIANS( 6.66 ) ) 
                   + SIN( RADIANS( 12.44 ) ) 
                   * SIN( RADIANS( lat ) ) 
                   ) 
      ) < 1
GROUP BY 
      b.id
ORDER BY 
      dcount DESC