How to check if user already in a database before inserting new user

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I have a winform 'register user', now before the form is submitted, i want to check the database if the username entered by the user is alredy in the database. if the username exist a messagebox should be displayed else the form is submitted.pls code wil b of great help tanx in advance

Posted 6-Sep-12 21:18pm

Ese ochuko

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_Amy · Answer 1 · 2012-09-06T21:28:00

Solution 3

You can use SQL EXIST to check whether the UserID exists in your table or not.
Use this command to check if the user is already exists:

SQL

DECLARE UserID VARCHAR(20) = 'test@test.com'
IF EXIST(SELECT * FROM tbUser WHERE UserID = @UserID)
BEGIN
    Print 'User Already Exist'
END
ELSE
BEGIN
    INSERT INTO tbUser VALUES(@UserID, 'Other Column Value')
END

--Amit

Posted 6-Sep-12 21:28pm

_Amy

Comments

ridoy 7-Sep-12 3:48am

correct..+5

_Amy 7-Sep-12 4:37am

Thank you ridoy. :)

Ese ochuko 9-Sep-12 3:44am

Hi thanks for your response, am using sqlserver an i am linkin my winform to it,this code u gave me where am i going to place it. Can you help me with a step by step example so i can undastand it more clearly.thaaaaaannnnnkkkss

Rickin Kane · Answer 2 · 2012-09-06T21:23:00

Solution 1

Create a SP and return a result in dataset , then check if dataset has rows , if row count =1 then user exists

Something like this

C#

Dataset dscheckuser=checkexists (txtusername.Text.Trim)
if(dscheckuser.table[0].rows.count > 0)
{
   // user exists 
}else
{
   // insert new user
}

Posted 6-Sep-12 21:23pm

Rickin Kane

Updated 6-Sep-12 21:29pm

v2

Comments

Ese ochuko 10-Sep-12 1:22am

Hithanks for your reply.you knw i have not done this bfore. in the code you gave to me, visual studio is not recognising the 'checkexist' is it a key word or what?. Can you please xplain the code with comment.thank you very much

__TR__ · Answer 3 · 2012-09-06T21:26:00

One way to do it would be write a stored procedure that takes user ID as parameter and checks to see if its in the database.
Here is a sample

SQL

CREATE PROCEDURE usp_CheckUserExists
@UserID INT

AS
BEGIN

DECLARE @UserExists BIT

IF EXISTS(SELECT 1 FROM [Your User Table] WHERE UserID = @UserID)
BEGIN
    SET @UserExists = 1
END
ELSE
BEGIN
    SET @UserExists = 0
END

SELECT @UserExists AS UserExists

END

The SP returns true or false based on whether the user ID exists or not. You can take this result in your application to check if the user ID exists before creating the user.