Basics and some tips on writing joins in T-SQL

Link to article on Joins in T-SQl : Basics

sqlteam.com

Points
1) when using aggregates with joins take care to include the column, as aggregating on '*' i.e. the row, might return false result specially for columns with null values.
2) when executing multiple joins using the left outer joins may be useful as using inner join might not return some rows with NULL values in the intermediate table.