T-SQL - Aliasing using "=" versus "as"

sql, sql-server, t-sql

Solution

‘=’ isn't valid ANSI SQL, so you'll have difficulty should you wish to run your application on a different DBMS.

(It's when ANSI form is used but the optional ‘AS’ is omitted I find the results difficult to read, personally.)

Problem

Is there any particular reason (performance or otherwise) to use AS ahead of = when aliasing a column? My current approach (for readability) is to use this: ``` select alias1 = somecolumn alias2 = anothercolumn from tables etc... ``` instead of this: ``` select somecolumn as alias1 anothercolumn as alias2 from tables etc... ``` Is there a performance or maintainability reason to use one over the other?

Original source