Good article. I just want to present a style of coding that prevents this situation. I often work with queries involving a dozen tables. Notice that each table is basically a separate select statement. If I didn't code in my style, I'd quickly get confused.

select

p.*,

c.*

FROM

(-- professor data

SELECT

Professor.Id AS [Id],

Professor.ProfessorName,

CASE Professor.HasTenure WHEN 1 THEN 'True' WHEN 0 THEN 'False' ELSE NULL END AS [Has Tenure]

FROM Professor

WHERE Professor.HasTenure = 'True'

) as P

left outer join

(-- class data

SELECT

Class.ProfessorId AS [ProfessorId],

Class.ClassName,

Class.ClassYear,

Class.ClassSemester

FROM Class

WHERE Class.ClassYear >= 2011

) as c on p.Id = c.ProfessorId