Question

I’m not sure what I am doing wrong. This is a sample query from a T-SQL Fundamentals book that I am reading…

SELECT empid, orderdate FROM Sales.Orders
WHERE custid = 71
GROUP BY empid, YEAR(orderdate)

I get the following error:

Msg 8120, Level 16, State 1, Line 1 Column ‘Sales.Orders.orderdate’ is
invalid in the select list because it is not contained in either an
aggregate function or the GROUP BY clause.

What the heck am I doing wrong?…

Answer 1

The GROUP BY you provided is working off empid and the year of the orderdate (an INT). But the SELECT is returning empid and a DATETIME data type… Disregarding the data type, the data is different between what is being grouped & presented.

You need to use:

  SELECT o.empid, 
         YEAR(o.orderdate) 
    FROM Sales.Orders o
   WHERE o.custid = 71
GROUP BY o.empid, YEAR(o.orderdate)

…or:

  SELECT o.empid, 
         o.orderdate 
    FROM Sales.Orders o
   WHERE o.custid = 71
GROUP BY o.empid, o.orderdate

Alternately, SQL Server allows you to reference column aliases in the GROUP BY:

  SELECT o.empid, 
         YEAR(o.orderdate) AS yr
    FROM Sales.Orders o
   WHERE o.custid = 71
GROUP BY o.empid, yr