Common Table Expressions in SQL

Tips:

• sql column with spaces
• group by aggregate over string column

References:

• http://stackoverflow.com/questions/5375634/can-i-use-multiple-with
• http://stackoverflow.com/questions/4740748/when-to-use-common-table-expression-cte
• https://msdn.microsoft.com/en-us/library/ms175972.aspx
• https://technet.microsoft.com/en-us/library/ms190766(v=sql.105).aspx