I don't know all of the syntax from all languages, but I do know that in Sybase and Microsoft SQL Server, the first would generate a syntax error. The HAVING an

I don't know all of the syntax from all languages, but I do know that in Sybase and Microsoft SQL Server, the first would generate a syntax error. The HAVING and WHERE clauses cannot reference column aliases. You could rewrite it to be: ... having sum(line_value) > 100; Would the performance be the same? That's up to the individual DB. To say, "Yes, they would" implies that all DBMS vendors implement query plans the same way. I think that, fundamentally, they should perform the same way but again: it's not up to you or I; it's up to the people who wrote the query execution engine.