Does Insert affects the Selects? | SQL Server Performance Forums

SQL Server Performance Forum – Threads Archive

Does Insert affects the Selects?

If some Insertion (15000 records) are being done into a table and at the same time user(s) are getting some information from that table (SELECT), then what happens to the user(s)? Do they experience slow down in retrieving their data? I don’t think there would be any lock involved but do the user(s) have to wait until the insertion is completed? In general, what is the SQL behavior?
It depends on the Isolation level – see Books online. You could perform a select statment with nolock and the select would happen without delay: Example: SELECT * FROM MyTable (NOLOCK) WHERE COL1 = 1
As Simon said, this depends on the isolation level. By default SQL Server uses READ COMMITTED, which means that the just inserted data can be seen by users once the transaction is successfully finished and the system is in a stable state again. But during that time, your users always can see the already existing data. —
Frank Kalis
Microsoft SQL Server MVP
Ich unterstütze PASS Deutschland e.V. for relevancy. Satya SKJ
This posting is provided “AS IS” with no rights for the sake of knowledge sharing.