![]() The _$operation value is 1 for a delete, 5 when the net operation is an insert or an update. The parameter can have the following values:Īll – returns the LSN of the final change, the _$update_mask column is always NULLĪll with mask – returns the LSN of the final change, the _$update_mask column shows the IDs of the modified columnsĪll with merge – returns the LSN of the final change. While the cdc.fn_cdc_get_net_changes function returns only one For example, if a column was first updated from ’1970 Napa Street’ to ‘123 Street’ and then to ‘99 Daisy Street’, the cdc.fn_cdc_get_all_changes function returns all 3 transactions The rows with a single change are represented the same way as with the cdc.fn_cdc_get_all_changes function. fn_cdc_get_net_changes_capture_instance ( from_lsn, to_lsn, '' ) ![]() We will describe and show examples for the ones most frequently used Ĭdc.fn_cdc_get_all_changes_ – returns a row for each change in the source table that belongs to the Log Sequence Number in the range specified by the input parametersĬdc. The same as with the SQL Server Change Tracking feature, the change information in SQL Server Change Data Capture is available through table valued functions. _$update_mask – similar to the update mask available in Change Tracking, a bit mask used to identify the ordinals of the modified columns The system table valued functions _$operation – indicates the change type made on the row _$seqval – the sequence value used to order the row changes within a transaction _$end_lsn – the column is always NULL in SQL Server 2012, future compatibility is not guarantee Every change committed in the same transaction has its own row in the change table, but the same _$start_lsn _$start_lsn – the Log Sequence Number of the commited transaction. The first five columns contain the metadata necessary for the feature, the rest are the exact replica of the source table To query the table, use the cdc.fn_cdc_get_all_changes and cdc.fn_cdc_get_net_changes functions The first one is identical to the row before the update, and the second one to the row after the update. The table contains a row for each insert and delete on the source table, and two rows for each update. ![]() ![]() When the feature is enabled on a table, the change table named cdc._CT is automatically created in the tracked database. The table dbo.cdc_jobs that stores configuration parameters for capture and cleanup jobs is the only system table created in the msdb database It maps Log Sequence Number values to the time the transaction was committed The index columns are used to uniquely identify rows in the source tablesĬdc.lsn_time_mapping – contains a row for each transaction in the source tables. The following tables are automatically created in the tracked database when Change Data Capture is enabled:Ĭdc.captured_columns – contains a row for each column tracked in the tracked (source) tablesĬdc.change_tables – contains a row for each change table in the tracked databaseĬdc.ddl_history – contains a row for each structure (Data Definition Language) change of source tablesĬdc.index_columns – contains a row for each index column associated with a change table. Now, we will analyze the records stored in change tables and describe the methods to read them In the previous article, How to enable and use SQL Server Change Data Capture, we described the main features of SQL Server Change Data Capture and showed how to set it up.
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