why do we write @ before writing a sql query ?

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i have a Doubt in mind about the use of @ in sql squeries
although we can use @ in parametrized query also like this --

insert into EMP (EmpName , Salary) values (@EmpName,@Salary) -- i think here @ is used for userInput ,but i dont get why @ is used in below code ???

VB

string _Insert = @"insert into Details(fName,lName,DOB,City) Values('" + fName_Txt.Text + "','" + lName_Txt.Text + "','" +_Date.ToString() + "','" + City_Txt.Text + "')";

pls help ..thanks in advance

Posted 10-Mar-13 18:17pm

sr_24

Updated 10-Mar-13 18:31pm

gvprabu

v2

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3 solutions

Solution 3

btw, lastly, as a matter of good form, I'd parameterise the SQL statement and avoid building it like this - you leave yourself open to 'SQL Injection' - google it

the short version is "what if someone deliberatly entered ';drop table x cascade' (for example) and that was added into the SQL starement and executed ?"

.. just saying

'g'

Posted 10-Mar-13 23:10pm

Garth J Lancaster

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Garth J Lancaster · Accepted Answer · 2013-03-10T18:29:00

Solution 1

Its a C# thing - it means interpret the string literally or 'as is' .. that is to say

C#

String myFilePath1 = @"Drive:\Path\File.Ext";

Won't cause an error - the "\P" and "\F" are not interpreted, but

C#

String myFilePath2 = "Drive:\Path\File.Ext";

WILL cause an error because "\P" and "\F" are not recognised/a valid escape sequence - you have to make it

C#

String myFilePath2 = "Drive:\\Path\\File.Ext";

without the '@' sign

'g'

Posted 10-Mar-13 18:29pm

Garth J Lancaster

Comments

Aarti Meswania 11-Mar-13 1:13am

5+ :)

sr_24 11-Mar-13 1:46am

thankyou very much awesome explaination ...So can iu conclude by it that -- Is it optional to use when initializing/declaring a string variable , if the string does not contain \p ,\f ..i can skip @

otherwise i hv to use it .. ?????
Is their any other reason also ..as my query does not have any \f , \p

Garth J Lancaster 11-Mar-13 5:03am

I think this post sums up the escape sequences - if you avoid those, you're unlikely to need the '@' http://msdn.microsoft.com/en-us/library/h21280bw.aspx

[modified] .. there's also, iirc, '\unnnn' for a unicode sequence of nnnn

rohitdon007 · Accepted Answer · 2013-03-10T19:35:00

Solution 2

@ sign stands for a variable in SQL server
Its scope is Limited to the batch in which it is used.

So if you are passing (@EmpName,@Salary) to the the sql, it means you are passing some variables to SQL in the form of parameters.

Posted 10-Mar-13 19:35pm

rohitdon007

Comments

sr_24 11-Mar-13 1:47am

thanks for the reply .... but why we use it before a string like-- ??

string _Insert = @"insert into Details(fName,lName,DOB,City) Values('" + fName_Txt.Text + "','" + lName_Txt.Text + "','" +_Date.ToString() + "','" + City_Txt.Text + "')";

rohitdon007 11-Mar-13 1:52am

it is not necessary always to use @ before a string, the main purpose of using @ is to just nullify some special characters like "\".

if we want to use "\", we have to write "\\" or we can use @"\"

sr_24 11-Mar-13 3:04am

thaanks