Error: Invalid expression in the select list (not contained in either an aggregate function or the GROUP BY clause)

Question

I am using Firebird SQL. The below mentioned query returns 4 rows as shown in the figure.

    SELECT a.EPS_ID,b.C_NAME,c.AY_YR_NAME,d.S_NAME,e.E_NAME
FROM 
    TBLEXAMPLANNER_S_MSB a, 
    TBLCLASS_MSB b, 
    TBLACADEMICYEAR_MSB c, 
    TBLSUBJECTS_MSB d, 
    TBLEXAMTYPE_MSB e
WHERE 
    a.EPS_CLASS_ID=b.C_ID 
AND a.EPS_SESSION_ID=c.AY_ID 
AND a.EPS_SUB_ID=d.S_ID 
AND a.EPS_PE_ID=e.E_ID

I want it to return only 1(one) row like

EPS_ID     C_NAME    AY_YR_NAME   S_NAME   E_NAME
---------------------------------------------------
7          5         2016-2017    English  FA1 

I am using the following query but it does not work.

SELECT a.EPS_ID,MAX(b.C_NAME) AS XT,c.AY_YR_NAME,d.S_NAME,e.E_NAME
FROM 
    TBLEXAMPLANNER_S_MSB a, 
    TBLCLASS_MSB b, 
    TBLACADEMICYEAR_MSB c, 
    TBLSUBJECTS_MSB d, 
    TBLEXAMTYPE_MSB e
WHERE 
    a.EPS_CLASS_ID=b.C_ID 
AND a.EPS_SESSION_ID=c.AY_ID 
AND a.EPS_SUB_ID=d.S_ID 
AND a.EPS_PE_ID=e.E_ID
GROUP BY a.EPS_ID,d.S_NAME

The error message is :

Invalid expression in the select list (not contained in either an aggregate function or the GROUP BY clause)

Answer 1

The usage of GROUP BY makes the engine group the records for you. To do grouping, you have to give advice to the RDBMS for each column, what it should do.

• Group it? -> Add column to GROUP BY-Clause
• Not group it? -> ok, what else?
  • ignore the column? remove it from your select-clause
  • Sum it? -> use SUM(mycol)
  • other aggregation functions can be found in the documentation

Additionally: In your case you try to group by EPS_ID, which is unique in each row. So a grouping by that column will return all rows, because there is nothing to group by. To group records, they have to have the same value.

Answer 2

Learn to use proper, explicit JOIN syntax.

Your problem is that all unaggregated columns need to be in the GROUP BY:

SELECT a.EPS_ID, MAX(b.C_NAME) AS XT, c.AY_YR_NAME, d.S_NAME, e.E_NAME
FROM TBLEXAMPLANNER_S_MSB a JOIN 
     TBLCLASS_MSB b
     ON a.EPS_CLASS_ID = b.C_ID JOIN
     TBLACADEMICYEAR_MSB c
     ON a.EPS_SESSION_ID = c.AY_ID JOIN
     TBLSUBJECTS_MSB d
     ON a.EPS_SUB_ID = d.S_ID JOIN 
     TBLEXAMTYPE_MSB e
     ON a.EPS_PE_ID = e.E_ID
GROUP BY a.EPS_ID, c.AY_YR_NAME, d.S_NAME, e.E_NAME;

Note: I would also recommend that you use table abbreviations for table aliases. So, ep for TBLEXAMPLANNER_S_MSB instead of a. Arbitrary table aliases make the query hard to follow.

Answer 3

Try

SELECT a.EPS_ID,c.AY_YR_NAME,d.S_NAME,e.E_NAME,MAX(b.C_NAME) AS XT ...
GROUP BY 1,2,3,4