Igor Micev (6/23/2016)
ashwan (6/23/2016)
let say there is a DB with large update frequently . In this situation all select statements are waiting for new update. ? why Select statements do not return with old values until all updates are committed?You can have the old values using the NOLOCK hint, but consider reading dirty data.
Read uncommitted isn't guaranteed to read the old values, it'll read whatever's there at the time the select reads the row. It's read committed snapshot (and snapshot) that see the old version until the update has completely finished.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability