Difference between SELECT function() AS column and SELECT function() column

Question

What is the difference between for instance:

SELECT coalesce(a,b,c) AS d from table;

and

SELECT coalesce(a,b,c) d from table;

both returns the same result. Does it means that AS is optional?

If everything else fails, read the manual: postgresql.org/docs/current/static/… — user330315
– user330315, Commented Jan 28, 2015 at 13:07
@a_horse_with_no_name when you dont know what to look for, searching for the keyword AS in hundreds of pages of doc is helpless — Below the Radar
– Below the Radar, Commented Jan 28, 2015 at 13:12
When looking at a manual, you shouldn't be searching for keywords. The way I find things like that is to check the table of contents and then think which part might cover my question. As this is about a SELECT statement, Chapter 7 "Queries" looks like a good starting point. Then I open that, and I see a chapter "Select List Items" - and there you go. Reading a manual is not the same as using a search engine. Finding your way around manuals is just as important as learning the actual technology — user330315
– user330315, Commented Jan 28, 2015 at 13:17

jpw · Accepted Answer · 2015-01-28 13:06:49Z

3

Yes, it is optional. From the documentation: "The AS keyword is optional, but only if the new column name does not match any PostgreSQL keyword"

answered Jan 28, 2015 at 13:06

jpw

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2 Comments

Thank you is this valid for any version?

@BelowtheRadar I would guess it is, although I haven't read the documentation for older versions.