Microsoft Access Merge Tables

Merging the two tables into one completely defeats the purpose of using a database and you're better off using excel at that point. You want to split the data as much as possible along logical lines so that you can find, say. All the orders that Mr X has ever made for a specific product.

One of the most powerful features of Total Access Detective is its ability to combine (merge) data between the two tables you compared. This is extremely useful for reconciling changes made to two copies of the same table.

Pdf
  • Home topics microsoft access / vba questions merge multiple tables to one table ms access Post your question to a community of 468,037 developers. It's quick & easy.
  • Use a table or query as the data source Open the source database, and in the Navigation Pane, select the table or query that you want use as the mail merge data source. On the External Data tab, in the Export group, click Word Merge. The Microsoft Word Mail Merge Wizard starts.

After Total Access Detective finds different records between your Microsoft Access tables, view the results and press the [Combine] button:

Options for Combining Records from Two Tables

A variety of options let you specify how the table should be created and populated:


Options for Merging Data from Two Tables

The example above is from comparing two tables in your current database. For two database comparison, the table names are identical and you specify the database where the new table is created. All the other options are identical:

Table Name

The name of the new table. You are prompted to overwrite it if it exists.

Create New Table From

Specify which of the two source tables becomes the design of the new table. The new table uses this source's field names, properties, indexes, etc.

Records to Include

Microsoft Access Merge Tables Cheat

You can optionally decide which records to include in the new table:

  • All identical records
  • New records in table 1 (they don't exist in table 2)
  • New records in table 2 (they don't exist in table 1)
  • Modified records. If you choose this, specify whether you want the changed record from table 1 or 2.

When you press [OK] the new table is created in your database.

Microsoft Access Merge Tables

Additional Resource

-->

Definition

Merge the specified DataTable with the current DataTable.

Overloads

Merge(DataTable, Boolean, MissingSchemaAction)

Merge the specified DataTable with the current DataTable, indicating whether to preserve changes and how to handle missing schema in the current DataTable.

Merge(DataTable, Boolean)

Merge the specified DataTable with the current DataTable, indicating whether to preserve changes in the current DataTable.

Merge(DataTable)

Merge the specified DataTable with the current DataTable.

Examples

The following console application demonstrates the behavior of the missingSchemaAction parameter of the Merge method. This example creates two versions of the same table, modifying the schema for the second version. The code then attempts to merge the second table into the first.

Note

This example shows how to use one of the overloaded versions of Merge. For other examples that might be available, see the individual overload topics.

Remarks

The Merge method is used to merge two DataTable objects that have largely similar schemas. A merge is typically used on a client application to incorporate the latest changes from a data source into an existing DataTable. This allows the client application to have a refreshed DataTable with the latest data from the data source.

The merge operation takes into account only the original table, and the table to be merged. Child tables are not affected or included. If a table has one or more child tables, defined as part of a relationship, each child table must be merged individually.

Merge the specified DataTable with the current DataTable, indicating whether to preserve changes and how to handle missing schema in the current DataTable.

Parameters

table
DataTable

The DataTable to be merged with the current DataTable.

preserveChanges
Boolean

true, to preserve changes in the current DataTable; otherwise false.

missingSchemaAction
MissingSchemaAction

One of the MissingSchemaAction values.

Examples

The following console application demonstrates the behavior of the missingSchemaAction parameter of the Merge method. This example creates two versions of the same table, modifying the schema for the second version. The code then attempts to merge the second table into the first.

Remarks

The Merge method is used to merge two DataTable objects that have largely similar schemas. A merge is typically used on a client application to incorporate the latest changes from a data source into an existing DataTable. This allows the client application to have a refreshed DataTable with the latest data from the data source.

The merge operation takes into account only the original table, and the table to be merged. Child tables are not affected or included. If a table has one or more child tables, defined as part of a relationship, each child table must be merged individually.

The Merge method is typically called at the end of a series of procedures that involve validating changes, reconciling errors, updating the data source with the changes, and finally refreshing the existing DataTable.

When performing a merge, changes made to the existing data before the merge are preserved during the merge operation unless the developer specifies false for the preserveChanges parameter. If the preserveChanges parameter is set to true, incoming values do not overwrite existing values in the Current row version of the existing row. If the preserveChanges parameter is set to false, incoming values do overwrite the existing values in the Current row version of the existing row. For more information about row versions, see Row States and Row Versions.

In a client application, it is usual to have a single button that the user can click that gathers the changed data and validates it before sending it back to a middle tier component. In this scenario, the GetChanges method is first invoked. That method returns a second DataTable optimized for validating and merging. This second DataTable object contains only the DataTable and DataRow objects that were changed, resulting in a subset of the original DataTable. This subset is generally smaller, and thus this subset is more efficiently passed back to a middle tier component. The middle tier component then updates the original data source with the changes through stored procedures. The middle tier can then send back either a new DataTable that includes original data and the latest data from the data source (by running the original query again), or it can send back the subset with any changes that have been made to it from the data source. (For example, if the data source automatically creates unique primary key values, these values can be propagated back to the client application.) In either case, the returned DataTable can be merged back into the client application's original DataTable with the Merge method.

When the Merge method is called, the schemas of the two DataTable objects are compared, because it is possible that the schemas may have been changed. For example, in a business-to-business scenario, new columns may have been added to an XML schema by an automated process. If the source DataTable contains schema elements (added DataColumn objects) that are missing in the target, the schema elements can be added to the target by setting the missingSchemaAction argument to MissingSchemaAction.Add. In that case, the merged DataTable contains the added schema and data.

After merging schemas, the data is merged.

When merging a new source DataTable into the target, any source rows with a DataRowState value of Unchanged, Modified, or Deleted are matched to target rows with the same primary key values. Source rows with a DataRowState value of Added are matched to new target rows with the same primary key values as the new source rows.

See also

Merge the specified DataTable with the current DataTable, indicating whether to preserve changes in the current DataTable.

Microsoft access merge tables using

Parameters

table
DataTable

The DataTable to be merged with the current DataTable.

preserveChanges
Boolean

true, to preserve changes in the current DataTable; otherwise false.

Examples

The following console application creates a DataTable containing rows, modifies some of the data in those rows, and attempts to merge data from a different DataTable. The example demonstrates the different behaviors for the preserveChanges parameter.

Remarks

Access Merge Tables Into One

The Merge method is used to merge two DataTable objects that have largely similar schemas. A merge is typically used on a client application to incorporate the latest changes from a data source into an existing DataTable. This allows the client application to have a refreshed DataTable with the latest data from the data source.

The merge operation takes into account only the original table, and the table to be merged. Child tables are not affected or included. If a table has one or more child tables, defined as part of a relationship, each child table must be merged individually.

The Merge method is typically called at the end of a series of procedures that involve validating changes, reconciling errors, updating the data source with the changes, and finally refreshing the existing DataTable.

Microsoft Access Merge Tables Examples

When performing a merge, changes made to the existing data before the merge are preserved during the merge operation unless the developer specifies false for the preserveChanges parameter. If the preserveChanges parameter is set to true, incoming values do not overwrite existing values in the Current row version of the existing row. If the preserveChanges parameter is set to false, incoming values do overwrite the existing values in the Current row version of the existing row. For more information about row versions, see Row States and Row Versions.

Microsoft Access Merge Tables

In a client application, it is usual to have a single button that the user can click that gathers the changed data and validates it before sending it back to a middle tier component. In this scenario, the GetChanges method is first invoked. That method returns a second DataTable optimized for validating and merging. This second DataTable object contains only the DataTable and DataRow objects that were changed, resulting in a subset of the original DataTable. This subset is generally smaller, and thus this subset is more efficiently passed back to a middle tier component. The middle tier component then updates the original data source with the changes through stored procedures. The middle tier can then send back either a new DataTable that includes original data and the latest data from the data source (by running the original query again), or it can send back the subset with any changes that have been made to it from the data source. (For example, if the data source automatically creates unique primary key values, these values can be propagated back to the client application.) In either case, the returned DataTable can be merged back into the client application's original DataTable with the Merge method.

When merging a new source DataTable into the target, any source rows with a DataRowState value of Unchanged, Modified, or Deleted are matched to target rows with the same primary key values. Source rows with a DataRowState value of Added are matched to new target rows with the same primary key values as the new source rows.

See also

Merge the specified DataTable with the current DataTable.

Parameters

table
DataTable

The DataTable to be merged with the current DataTable.

Examples

The following console application creates a simple DataTable and adds data to the table. The example then creates a copy of the table, adding rows to the copy. Finally, the example calls the Merge method to merge the data in the second table with the data in the first table.

Remarks

The Merge method is used to merge two DataTable objects that have largely similar schemas. A merge is typically used on a client application to incorporate the latest changes from a data source into an existing DataTable. This allows the client application to have a refreshed DataTable with the latest data from the data source.

The merge operation takes into account only the original table, and the table to be merged. Child tables are not affected or included. If a table has one or more child tables, defined as part of a relationship, each child table must be merged individually.

The Merge method is typically called at the end of a series of procedures that involve validating changes, reconciling errors, updating the data source with the changes, and finally refreshing the existing DataTable.

When performing a merge, changes made to the existing data before the merge are preserved by default during the merge operation. Developers can modify this behavior by calling one of the other two overloads for this method, and specifying a false value for the preserveChanges parameter.

In a client application, it is usual to have a single button that the user can click that gathers the changed data and validates it before sending it back to a middle tier component. In this scenario, the GetChanges method is first invoked. That method returns a second DataTable optimized for validating and merging. This second DataTable object contains only the DataRow objects that were changed, resulting in a subset of the original DataTable. This subset is generally smaller and thus more efficiently passed back to a middle tier component. The middle tier component then updates the original data source with the changes through stored procedures. The middle tier can then send back either a new DataTable that includes original data and the latest data from the data source (by running the original query again), or it can send back the subset with any changes that have been made to it from the data source. (For example, if the data source automatically creates unique primary key values, these values can be propagated back to the client application.) In either case, the returned DataTable can be merged back into the client application's original DataTable with the Merge method.

When merging a new source DataTable into the target, any source rows with a DataRowState value of Unchanged, Modified, or Deleted, is matched to target rows with the same primary key values. Source rows with a DataRowState value of Added are matched to new target rows with the same primary key values as the new source rows.

Access

Microsoft Access Merge Tables Online

See also