what is select 'X'?

Question

what is select 'X'?

deepikamm

SSCommitted

Points: 1681
More actions
January 6, 2011 at 2:50 am

#232733

can anyone explain me the functionality of "select x from tablename"?

Viewing 12 posts - 1 through 11 (of 11 total)

You must be logged in to reply to this topic. Login to reply

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 1

It returns the column X for all rows in table tablename

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

deepikamm SSCommitted Points: 1681 More actions · Answer 2

why do people make use of "select x" instead of "select columnname"?

psingla Hall of Fame Points: 3840 More actions · Answer 3

in topic you have specified select 'x'

so i think you wanted to know for select 'x' from tablename

the above query will return char x for all the records in the table.

normally stmts like these are used with exists/not exists

so instead of fetching all the columns in case where you want weather the data exists or not ,,simply use something like 'x',1 ,,

this will reduce the traffic and use less memory.

Pramod
SQL Server DBA | MCSE SQL Server 2012/2014
in.linkedin.com/in/pramodsingla/
http://pramodsingla.wordpress.com/

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 4

deepikamm (1/6/2011)
why do people make use of "select x" instead of "select columnname"?

Errr, they don't. Select x is only possible if there's a column called x, otherwise it will throw an error.

Can you explain clearer what you're asking about?

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

deepikamm SSCommitted Points: 1681 More actions · Answer 5

yes thats wat am asking..so it is generally used with if exixts/not exists to check for the exixtence of rows..am i correct?

psingla Hall of Fame Points: 3840 More actions · Answer 6

yes

Pramod
SQL Server DBA | MCSE SQL Server 2012/2014
in.linkedin.com/in/pramodsingla/
http://pramodsingla.wordpress.com/

deepikamm SSCommitted Points: 1681 More actions · Answer 7

@gila: i hav seen queries like" if exists ( select 'x' from tablename)" actaully i meant this query only.

deepikamm SSCommitted Points: 1681 More actions · Answer 8

deepikamm

SSCommitted

Points: 1681

January 6, 2011 at 3:32 am

#1269969

thank u..:)

Henrico Bekker One Orange Chip Points: 27652 More actions · Answer 9

Is this query is SQL or VB?

in SQL you might find a: Select @x from..... if @x was declared as a variable.

but normal Select x .... means X is your column name.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
This thing is addressing problems that dont exist. Its solution-ism at its worst. We are dumbing down machines that are inherently superior. - Gilfoyle

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 10

deepikamm (1/6/2011)
@gila: i hav seen queries like" if exists ( select 'x' from tablename)" actaully i meant this query only.

There's a massive difference between SELECT 'x' from table and SELECT x from table.

SELECT 'x' from table returns the constant value x for all rows. It's often used in EXISTS because the EXISTS predicate doesn't care about values, it's only concerned about whether or not there's a row.

SELECT x from table returns the column named x from the table, or an error if there is no column named x.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

deepikamm SSCommitted Points: 1681 More actions · Answer 11

deepikamm

SSCommitted

Points: 1681

January 6, 2011 at 4:20 am

#1269982

am clear now..