CODEWITHSUNDEEP
sqlmysqldatabasecolumn-alias
Ben
Ben

Reputation: 11208

Column alias not recognized in WHERE-statement

I have a strange 'problem' with one of my created queries. Given the next query:

 SELECT 
 ID,
 DistanceFromUtrecht,
 (
  SELECT
   (MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24))
  FROM
   PricePeriod
  WHERE
   PricePeriod.FK_Accommodation = Accommodation.ID
 ) AS LatestBookableTimestamp
FROM
 Accommodation
WHERE
 LatestBookableTimestamp < UNIX_TIMESTAMP()

phpMyAdmin keeps throwing an error about not having a column named 'LatestBookableTimestamp', even allthough I've a column, retreived by a subquery, that alias. I've also tried it selecting every column with the tableprefix. This didn't work eighter. Finally I've selected all columns by a table-alias and I gave the table an alias. All with no luck.

Can someone tell me what I'm doing wrong? I've even searched for some resources to see if I'm not mistaken, but in many cases authors on the internet use the same syntax as I do.

Upvotes: 4

Views: 9496

Answers (4)

D&#39;Arcy Rittich
D&#39;Arcy Rittich

Reputation: 171559

select a.ID, 
    a.DistanceFromUtrecht, MaxDateUntil - (ReleaseDays * 60 * 60 * 24) AS LatestBookableTimestamp 
from (
    SELECT FK_Accommodation, MAX(DateUntil) as MaxDateUntil
    FROM PricePeriod 
    group by FK_Accommodation
) ppm
inner join Accommodation a on ppm.FK_Accommodation = a.ID 
where MaxDateUntil - (ReleaseDays * 60 * 60 * 24) < UNIX_TIMESTAMP()

Upvotes: 1

Mchl
Mchl

Reputation: 62395

Use HAVING 

HAVING
  LatestBookableTimestamp < UNIX_TIMESTAMP()

On a side note, you're using a dependednt subquery, which is a bad idea performance wise.

Try like this:

SELECT 
  a.ID,
  a.DistanceFromUtrecht,
  pp.LatestBookableTimestamp
FROM
  Accommodation AS a
INNER JOIN (
  SELECT
    FK_Accommodation,
    MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24) AS LatestBookableTimestamp
  FROM 
    PricePeriod 
  GROUP BY 
    FK_Accommodation
) AS pp    
ON pp.FK_Accommodation = a.ID    
WHERE
  pp.LatestBookableTimestamp < UNIX_TIMESTAMP()

Upvotes: 11

Fosco
Fosco

Reputation: 38526

You would need to take the original query, without the where clause, and turn that into a sub query. 

select * from (
 SELECT ID, DistanceFromUtrecht, 
 ( 
  SELECT 
   (MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24)) 
  FROM 
   PricePeriod 
  WHERE 
   PricePeriod.FK_Accommodation = Accommodation.ID 
 ) AS LatestBookableTimestamp 
FROM 
 Accommodation 
) a
WHERE 
 LatestBookableTimestamp < UNIX_TIMESTAMP()

Upvotes: 1

OMG Ponies
OMG Ponies

Reputation: 332731

You can't use a column alias in the WHERE clause.
MySQL (and SQL Server) will allow column alias use in the GROUP BY, but it's not widely supported. ORDER BY is the most consistently supported place that supports column alias referencing.

Use:

   SELECT a.id,
          a.distancefromutrecht,
          b.LatestBookableTimestamp
     FROM ACCOMMODATION a
LEFT JOIN (SELECT pp.fk_accommodation,
                  MAX(DateUntil) - (ReleaseDays * 60 * 60 * 24) AS LatestBookableTimestamp
             FROM PRICEPERIOD pp
         GROUP BY pp.fk_accommodation) b ON b.fk_accommodation = a.id
    WHERE b.LatestBookableTimestamp < UNIX_TIMESTAMP()

Upvotes: 7

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