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Editorial Team
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Asked: 2026-05-12T08:03:56+00:00

IF NOT EXISTS(SELECT * FROM MyTable WITH(nolock) WHERE Key = ‘MyKey’) INSERT MyTable(Key) Values(‘MyKey’)

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IF NOT EXISTS(SELECT * FROM MyTable WITH(nolock) WHERE Key = 'MyKey')
  INSERT MyTable(Key) Values('MyKey')

If The value does not exist in the table, does the query aquire a lock?

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1 Answer

  1. Editorial Team

    From the docs:

    READUNCOMMITTED and NOLOCK hints apply only to data locks. All queries, including those with READUNCOMMITTED and NOLOCK hints, acquire Sch-S (schema stability) locks during compilation and execution. Because of this, queries are blocked when a concurrent transaction holds a Sch-M (schema modification) lock on the table. For example, a data definition language (DDL) operation acquires a Sch-M lock before it modifies the schema information of the table. Any concurrent queries, including those running with READUNCOMMITTED or NOLOCK hints, are blocked when attempting to acquire a Sch-S lock. Conversely, a query holding a Sch-S lock blocks a concurrent transaction that attempts to acquire a Sch-M lock. For more information about lock behavior, see Lock Compatibility (Database Engine).

    So it won’t acquire a data lock, but it will still acquire a schema stability lock.

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