Sql lock table while updating
I explicitly do not commit there in order to keep the locks.In the second session I issue the same statement and of course that one waits due to locking.
The USE 'your DB' GO SELECT OBJECT_NAME(p.[object_id]) Blocked Object FROM sys.dm_exec_connections AS blocking INNER JOIN sys.dm_exec_requests blocked ON blocking.session_id = blocked.blocking_session_id INNER JOIN sys.dm_os_waiting_tasks waitstats ON waitstats.session_id = blocked.session_id INNER JOIN sys.partitions p ON SUBSTRING(resource_description, PATINDEX('%associated Object Id%', resource_description) 19, LEN(resource_description)) = p.partition_id SELECT db_name(rsc_dbid) AS 'DATABASE_NAME', case rsc_type when 1 then 'null' when 2 then 'DATABASE' WHEN 3 THEN 'FILE' WHEN 4 THEN 'INDEX' WHEN 5 THEN 'TABLE' WHEN 6 THEN 'PAGE' WHEN 7 THEN 'KEY' WHEN 8 THEN 'EXTEND' WHEN 9 THEN 'RID ( ROW ID)' WHEN 10 THEN 'APPLICATION' end AS 'REQUEST_TYPE', CASE req_ownertype WHEN 1 THEN 'TRANSACTION' WHEN 2 THEN 'CURSOR' WHEN 3 THEN 'SESSION' WHEN 4 THEN 'Ex SESSION' END AS 'REQUEST_OWNERTYPE', OBJECT_NAME(rsc_objid ,rsc_dbid) AS 'OBJECT_NAME', PROCESS.SQL Server can avoid taking shared row-level locks when there is no danger of reading uncommitted data without them (though higher-level Intent-Shared (IS) locks are still taken). In most cases, the row is 'unlocked' just before the server processes the next row.There are circumstances in which shared locks taken at the default isolation level are held to the end of the current statement, but not to the end of the table hint is almost always a bad idea. SQL Server takes locks when necessary to ensure it meets the semantic guarantees provided by the current isolation level.There are certainly times where it is useful to know a little bit about why locks are taken, but attempting to predict them is very often counter-productive.SQL Server provides a wide variety of isolation levels; choose the one that provides the guarantees and behaviours your data consumers need.
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It depends on the usage, but typically I recommend steering away from cursors, for performance and best practices. :) And if you're ever still unsure, if you're able to find a second set of eyes - that's saved a few too! -skibunnysqldiva CREATE #Temp IDs (ID BIGINT NOT NULL); declare @ids To Delete table (id bigint); insert into @ids To Delete select some Id from some Table with (nolock) where some Condition = 'some value'; WHILE (1 = 1) BEGIN BEGIN TRAN DELETE TOP (500) tmp OUTPUT DELETED.