可以 HAVING 评估字符串条件

Question

The following query totals sales in state= 'MA' for each salesperson.

SELECT salesperson_id, sum(sales)
FROM salesperson
GROUP BY salesperson_id
HAVING state = 'MA';


Incorrect Response : TRUE 
    
Correct Answer : FALSE

[Source: Hoffer et al Modern Database Management 13 ed., practice question]

The SQL statement apparently cannot display sales for state = 'MA' for each salesperson. Without recreating this in SQL server, I imagined this will be ok. Why would the answer be FALSE in this case? Thanks!

Context: I am going through some practices questions for the Hoffer et al textbook Modern Database Management (13 ed.), and I'm trying to understand the answer to this question.

Answer 1

If your purpose is to merely exclude any rows for any other state , you should place it in the WHERE clause. HAVING applies to the rows constructed after the GROUP BY (you only have salesperson_id & sum(sales) in the GROUP BY, so HAVING can only have conditions for these).

'state' must be in the GROUP BY for this to work; but this query is syntactically invalid. If you are not getting a syntax error it could be because state might be a reserved word in your dbms with a meaning/value other than 'MA', then you would get no errors, but no results, either.