Updating a specific row in sql
Updating a specific row in sql - Bengali webcam
This IS lock is then followed by an IX and X Lock made by the Insert.Both methods when Updating a row: When a row exist in a table we have to update it.
can you guess what happens to the update statement ? First, both of these methods could theoratically give you a wrong error.1. if rowcount = 0 insert- Lets assume two processes P1 and P2- Lets assume table TAB1 has row R1 Case 1.a (Row R1 does not exist)a. Try insert, then on exception of duplicate row, update.
The following code may work.create table saad_test ( pk int not null primary key, data varchar(100) )insert into saad_test values ( 1, 'saad' )set nocount ondeclare @v_pk int, @v_data varchar(100)beginset @v_pk = 1set @v_data = 'ahmad2'insert into saad_test values ( @v_pk, @v_data )-- error for duplicate is 2627if ( @@ERROR = 2627 )update saad_test set data = @v_data where pk = @v_pkend And I will prefer to use true exceptions if available. Probably alright for the RBAR necessary for a GUI, though. I need to be able to duplicate via a stored procedure a specific row in the table identified by primary key value i.e.
But even those do not cause any unnecessary overhead. Ran into this because of another forum with a link... insert a record form that table into the SAME table ....
Because I'm using a condition with 2 columns (receipt Bal, receipt Date) in a table called RECEIPTS.
But it seems like it's not doing what I want as it's inserting a new row even if it's already there.
P2 executes it at time T1 (insert is attempted, but because of P1 this will wait until P1 comits)c. P1 executes it at time T1 (insert will detect a duplicate)b.
If P1 commits, P2 will detect duplicate and do the update. P2 executes it at time T1 (insert will detect a duplicate)c. Don't think this can't happen; I actually noticied the issue in a high volume environment Saad [email protected] levels are not the right solution since the problem is in a high volume scenario where you do not want more isolation. And, as clever as it is, updating by exception error just doesn't sit right with me... insert has to be tried and failure detected and only then does the update occur. I have a table consisting of 200 fields with a primary key(auto-increment).
This question pops up a lot everywhere and it's a common business requirement and until SQL Server 2008 doesn't come out with its MERGE statement that will do that in one go we're stuck with 2 ways of achieving this.
The biggest problem with every update/insert (upsert for those who haven't heard the term yet) is locking. IX Lock (Intent Exclusive Lock) and X Lock(Exclusive Lock). If row exists update else insert First let's create our test table: When a row doesn't exist in a table we have to insert it.
Update .........=......where id [email protected] @found=0set @found = Select count(*) from ......
where [email protected] @found =0 --do INSERT--else exit The best way of solving this probably depends on your situation.
The NO EXISTS method is less expensive due to only one IX and X Lock made by the Update.