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sys.fn_cdc_is_bit_set (Transact-SQL)


Applies To: SQL Server 2014, SQL Server 2016 Preview

Indicates whether a captured column has been updated by checking whether its ordinal position is set within a provided bitmask.

Applies to: SQL Server (SQL Server 2008 through current version).

Topic link icon Transact-SQL Syntax Conventions

sys.fn_cdc_is_bit_set ( position , update_mask )


Is the ordinal position in the mask to check. position is int.


Is the mask identifying updated columns. update_mask is varbinary(128).

This function is typically used as part of a change data query to indicate whether a column has changed. In this scenario, the function sys.fn_cdc_get_column_ordinal is used before the query to obtain the required column ordinal. sys.fn_cdc_is_bit_set is then applied to each row of change data that is returned, providing the column-specific information as part of the returned result set.

We recommend using this function instead of the function sys.fn_cdc_has_column_changed when determining whether columns have changed for all rows of a returned result set.

Requires membership in the public role.

The following example uses sys.fn_cdc_is_bit_set to prepend to the result set generated by the query function cdc.fn_cdc_get_all_changes_HR_Department the column 'IsGroupNmUpdated' using the precomputed column ordinal and the value of __$update_mask as arguments to the call.

USE AdventureWorks2012;
DECLARE @from_lsn binary(10), @to_lsn binary(10), @GroupNm_ordinal int;
SET @from_lsn = sys.fn_cdc_get_min_lsn('HR_Department');
SET @to_lsn = sys.fn_cdc_get_max_lsn();
SET @GroupNm_ordinal = sys.fn_cdc_get_column_ordinal('HR_Department','GroupName');

SELECT sys.fn_cdc_is_bit_set(@GroupNm_ordinal,__$update_mask) as 'IsGroupNmUpdated', *
FROM cdc.fn_cdc_get_all_changes_HR_Department( @from_lsn, @to_lsn, 'all')
WHERE __$operation = 4;

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