How can I run update query from perl to update existing fields in column?

this is only update query... being executed..
If u want to stop insert query, comment out the execution of insert query by adding a hash in front of that.

eg.
#my $ins = $dbh->prepare("SOME INSERT QUERY");
#$ins->execute();

Try this..

$stmt = "UPDATE data SET diff=(time2 - time1) where username='testuser'";
 
# Prepare and execute the SQL query
$sth = $$dbh->prepare($$stmt) 
    || die "prepare: $$stmt: $DBI::errstr";
$sth->execute || die "execute: $$stmt: $DBI::errstr";

Select allOpen in new window

I dont have any insert query in my code

it is just this query when executed in sql query browser just updates the field and incase executed from perl also insert the field

Do you mean it inserts a row (record) or field?  If diff is NULL, and you want to keep it NULL, use this sql:
my $diff=$dbh->prepare("UPDATE data SET diff=(time2 - time1) where username='testuser' AND diff IS NOT NULL");

Is there any query in sql which update all the columns in case  given user is already existing in database

for ex...if I already have 'testuser' in database and If I try to 'insert' same user again , it should update the existing user corresponding columns

I think it can be done using duplicate key but not sure

http://dev.mysql.com/doc/refman/5.0/en/replace.html

>>Is there any query in sql which update all the columns in case  given user is already existing in database

>>for ex...if I already have 'testuser' in database and If I try to 'insert' same user again , it should update the existing user corresponding columns

You can try REPLACE statement

http://dev.mysql.com/doc/refman/5.0/en/replace.html

Oops.. not refreshed..

saini_er, Your initial question is still confusing, what is getting inserted !!

ghost_k8
Sorry for confusion.....my question is , I want to write a insert query(pls note it is little different from orignal question) which can check if the guven username already exist in database or not and incase it exists, it should just update  the corresponding field for that username for given values otherwsie should insert new row with that username and corresponding values

I am using this query
 and somehow it is inserting new row instead of updating existing one
my $user=$dbh->prepare('REPLACE INTO data(username,password) VALUES (?, ?)');
$user -> execute($username,$pass);

That means that $username for username and $pass for password are not a duplicate record.  Is username set as the primary key for the table?  If not, that would be the problem.