mysql: Unknown column in field list

Question

I am creating a procedure where I'm supposed to look for the last date of an exam.
So I created a local variable for this because I will need this date in other things as well. However, when I do a simple SELECT of this local variable, I get the message:

Unknown column 'last_exam' in 'field list'.

Code:

DECLARE latest_exam date;

  SELECT DATE(MAX(ex_date))
    INTO latest_exam
    FROM vets
   WHERE an_id = p_animal_id
GROUP BY an_id;

SELECT latest_exam, and a bunch of other stuff. ;

In the select, do I need to include a FROM clause? I didn't think so because I figured latest_exam is within the procedure.

Answer 1

you're not assigning the result of your select in the variable.

Do this

select latest_exam = date(max(ex_date))..

Answer 2

I think CROSS JOIN can answer your question since it produces cartesian product from both tables. Try this.

SELECT x.maxDate,
       b.*
FROM tableName b,
    (
        SELECT DATE (max(ex_date)) maxDate
        FROM vets
        WHERE an_id = p_animal_id
        GROUP BY an_id
    ) x

Answer 3

I had the same problem; it turned out not to be my SELECT INTO query within the procedure (which, yes, is valid in MySQL), but a call made later on in that outer procedure to another procedure with that actual error.

I only found this after confirming my query outside of the procedure with mock values:

SET @this_RID=0, @this_RANo=0, @this_modpos=0;

SELECT Response_ID, Response_attempt_No, position, UNCOMPRESS(RAMX.`data`)
INTO @this_RID, @this_RANo, @this_modpos, @this_XML 
FROM RAMX
WHERE 
    Response_ID>=@this_RID AND Response_attempt_No>=@this_RANo AND position>=@this_modpos 
    AND (NOT (Response_ID=@this_RID AND Response_attempt_No=@this_RANo AND position=@this_modpos))
    AND module_ID=2
    AND `data` <> ""    
ORDER BY Response_ID, Response_attempt_No, position
LIMIT 1;

SELECT @this_RID, @this_RANo, @this_modpos;

+-----------+------------+--------------+
| @this_RID | @this_RANo | @this_modpos |
+-----------+------------+--------------+
|    451994 |          0 |            1 |
+-----------+------------+--------------+
1 row in set (0.00 sec)

Calling the outer procedure was giving this error before correcting the procedure it called:

ERROR 1054 (42S22): Unknown column 'data' in 'field list'