Search in sql database

how to write 开发者_C百科an sql query to do: if the parameter is empty then it display all records, but if the parameter is not empty, it display the records for this value?

thank you

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SELECT *
    FROM YourTable
    WHERE (YourColumn = @Param OR @Param IS NULL)

However, this may not always be an optimal approach. See: Catch-all queries for one discussion.

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Another option:

WHERE Column1 = COALESCE(@Param, Column1)