Mapping Errors

This topic provides information that may help you to troubleshoot mapping errors. It provides information about using the Project Configuration dialog box and what happens to a project when the database schema changes.

When you create a new project and you specify the data sources you want to compare, SQL Data Compare selects all tables for comparison if:

the tables have similar structure
the table names and owner names are similar
the tables have suitable comparison keys

SQL Data Compare selects all columns for comparison if the column names are similar and the data types are compatible.

As you configure your project, for example when you select or clear a check box on the Tables & Views tab or the Remap Objects tab, SQL Data Compare records those changes. When you save the project, those configuration changes are saved in the project file.

When you open a project, or click a different tab on the Project Configuration dialog box, or click Refresh on the Tables & Views tab, SQL Data Compare plays back each project configuration change. If you cleared the check boxes for some of the tables and then you cleared the check boxes for some of the columns, SQL Data Compare attempts to clear those check boxes. If SQL Data Compare cannot replay any of the configuration changes, a warning symbol is displayed.

If the database schema has changed, and SQL Data Compare cannot replay any of the project configuration changes, the affected tables or columns will not be compared.

For example, if you clear the check box for a particular table, and that table is removed from the database schema, SQL Data Compare displays a warning symbol on the Tables & Views tab.

SQL Data Compare also shows a warning symbol on the Remap Objects tab, and in this example, the table's status is set to Unmapped.

If you ignore the warning and you run the comparison, SQL Data Compare compares only the tables for which there are no warnings; you will see a warning symbol in the direction bar in the main window, and in this example, the table is listed under tables or views that could not be compared.

How do I get rid of the warning symbol?

If you want to compare a table that is shown as Unmapped on the Remap Objects tab because it exists in only one of the data sources but not both, you must fix the database schema. Red Gate Software offers SQL Compare, which will synchronize the structure of two databases. You can then use SQL Data Compare to synchronize the data. To find out more about SQL Compare, visit www.red-gate.com.

If you do not want to compare an Unmapped table, you can still run the comparison and synchronization but the table will be excluded.

If the deleted column was set as the comparison key, you can select a different column for the comparison key so that you can include the table in the comparison.

What happens when a table is created or dropped?

If a new table has been added to the database schema since you last ran the comparison, SQL Data Compare will include the table in the comparison. However, if you excluded tables by clicking None on the Tables & Views tab, the new table will not be included in the comparison.

If a table is removed from the database schema since you last ran the comparison, SQL Data Compare will not display the table in the Project Configuration dialog box. However, if you made any configuration changes for that table, you will see a warning symbol on the Table & Views tab and the Remap Objects tab. The project configuration changes include:

selecting or clearing the table's check box
setting a different comparison key or custom comparison key for that table
setting WHERE clauses for that table
selecting or clearing the check boxes for any columns in that table
mapping any of the columns in that table
mapping that table using the Remap Objects tab
mapping schemas (owners)

What happens when a column is added or dropped?

If a new column has been added to a table since you last ran the comparison, SQL Data Compare will include the column in the comparison.

If a column has been removed from a table and you made any configuration changes for that column, you will see a warning symbol on the Table & Views tab and the Remap Objects tab. The project configuration changes include:

setting that column as a custom comparison key
selecting or clearing the check boxes for that column
mapping that column

Can I use a single project to compare and synchronize more than one database?

Yes. If you are using SQL Data Compare to synchronize data for all your databases with similar schemas, for example synchronizing development, quality assurance, user acceptance testing, training, or production databases, you can select each database in turn on the Data Sources tab, and run the comparison and the synchronization. If there are schema differences, your project configuration changes are retained but there may be some tables or columns that cannot be compared.