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    <p>Under what isolation level?</p> <p>For the write part (the insert) everything is the same no matter the isolation level: all inserted rows are locked in X mode until the end of the end of the transaction. Row locks may <a href="http://blogs.msdn.com/b/sqlserverstorageengine/archive/2006/05/17/lock-escalation.aspx" rel="nofollow">escalate</a> to table locks.</p> <p>If the isolation level is left at the default <strong>read committed</strong> and read-committed-snapshot-isolation option on the database is OFF the things will happen like this: each select will lock one row at a time in S mode and will release it immediately.</p> <p>Under <strong>repeatable read</strong> isolation the S locks acquired by the SELECTs will be retained until the end of the transaction, and they may escalate to table S locks.</p> <p>Under <strong>serializable read</strong> isolation the SELECTs will acquire range locks instead of row locks and will retain them till until the end of the transaction. Again, lock escalation may occur.</p> <p>Under <strong>snapshot isolation</strong> the SELECTs acquire no locks at all (ignoring some technicalities around schema stability locks), they will read any locked row from the versions tore instead. The version read corresponds to the snapshot of the value at the beginning of the transaction.</p> <p>Under read committed isolation when <strong>read-committed-snapshot-isolation</strong> is enabled on the database the SELECTs will not acquire any locks, they will read from the version store instead if a row is locked. The version read corresponds to the snapshot of the value at the beginning of the statement.</p> <p>Now back to your question, why do you see differences in performance? As with any performance question, it is best you apply a investigation methodology, and <a href="http://msdn.microsoft.com/en-us/library/cc966413.aspx" rel="nofollow">Waits and Queues</a> is an excellent one. Once you investigate the root cause, a proper solution can be proposed.</p>
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    1. POHow does SQL Server handle SELECT statements in a transactional INSERT?
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    1. USRemus Rusanu
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    1. COI thought that this rabbit hole went deeper than I thought. Thanks.
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      1. USBill Sempf
 

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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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