Guide to table relationships - Access
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Create a second dimension based on existing table, Fact Internet Sales. Although this is a fact table, it contains Sales Order information.What is DOMESTIC PARTNERSHIP? What does DOMESTIC PARTNERSHIP mean?
We'll use it to build a Sales Order dimension. In Specify Source Information, you will see a warning that indicates a Name column must be specified. Choose SalesOrderNumber as the Name. On the next page of the wizard, choose the attributes. In this example, you can select just SalesOrderNumber. Rename the dimension to Dim Sales Orders, so that you have a consistent naming convention for the dimensions.
Right-click Cubes and select New Cube. You are choosing FactInternetSales because it contains the measures you want to use in the cube. You are choosing FactInternetSalesReason because it is the intermediate measure group, providing member association data that relates sales orders to sales reasons.
Choose measures for each fact table. To simplify your model, clear all the measures, and then select just Sales Amount and Fact Internet Sales Count at the bottom of the list. The FactInternetSalesReason only has one measure, so it is selected for you automatically. You do not need this dimension, so you can clear it from the list.
Name the cube and click Finish. Recall that the following icon indicates a many-to-many relationship. You can see that this dialog box is used to specify a many-to-many relationship. If you were adding dimensions that had a regular relationship instead, you would use this dialog box to change it to many-to-many.
Deploy the project to an Analysis Services multidimensional instance. In the next step, you will browse the cube in Excel to verify its behaviors.
Testing Many-to-Many When you define a many-to-many relationship in a cube, testing is imperative to ensure queries return expected results. You should test the cube using the client application tool that will be used by end-users. In this next procedure, you will use Excel to connect to the cube and verify query results. Browse the cube in Excel Deploy the project and then browse the cube to confirm the aggregations are valid.
Enter the name of the server, choose the database and cube.
Create a PivotTable that uses the following: Because we are using sample data, the initial impression is that all sales orders have identical values. However, if you scroll down, you begin to see data variation. Part way down, you can find the sales amount and sales reasons for order number SO Grand total of this particular order is Notice that the Sales Amount is correctly calculated for the order; it is Why put a sales amount under each sales reason in the first place?
The answer is that it allows us to identify the amount of sales we can attribute to each reason. Scroll to the bottom of the worksheet.
It is now easy to see that Price is the most important reason for customer purchases, relative to other reasons as well as the grand total. Tips for handling unexpected query results Hide measures in the intermediate measure group, such as the count, that do not return meaningful results in a query. This prevents people from trying to use aggregations producing meaningless data. To hide a measure, set Visibility to False on the attribute in dimension designer. Create perspectives to use a subset of measures and dimensions that support the analytical experience you want to provide.
Possibly, a cube that contains many measure groups and dimensions do not work well together in all cases. By isolating the dimensions and measure groups that you intend to be used together, you ensure a more predictable outcome. Always remember to deploy and reconnect after changing a model.
If you have not yet defined any relationships, the Show Table dialog box automatically appears. If it does not appear, on the Design tab, in the Relationships group, click Show Table. The Show Table dialog box displays all of the tables and queries in the database. To see only tables, click Tables. To see only queries, click Queries. To see both tables and queries, click Both. Select one or more tables or queries and then click Add.
When you have finished adding tables and queries to the Relationships window, click Close. Drag a field typically the primary key from one table to the common field the foreign key in the other table. To drag multiple fields, press the CTRL key, click each field, and then drag them. The Edit Relationships dialog box appears. Verify that the field names shown are the common fields for the relationship.
If a field name is incorrect, click the field name and select a new field from the list. To enforce referential integrity for this relationship, select the Enforce Referential Integrity check box. For more information about referential integrity, see the Understanding Referential Integrity and the Enforce Referential Integrity sections.
The relationship line is drawn between the two tables. If you selected the Enforce Referential Integrity check box, the line appears thicker at each end. This means the Indexed property for these fields should be set to Yes No Duplicates.
If both fields have a unique index, Access creates a one-to-one relationship. This means the Indexed property for this field should be set to Yes No Duplicates. The field on the "many" side should not have a unique index. When one field has a unique index and the other does not, Access creates a one-to-many relationship.
Create a table relationship by using the Field List pane You can add a field to an existing table that is open in Datasheet view by dragging it from the Field List pane.
The Field List pane shows fields available in related tables and also fields available in other tables. When you drag a field from an "other" unrelated table and then complete the Lookup Wizard, a new one-to-many relationship is automatically created between the table in the Field List pane and the table to which you dragged the field.
This relationship, created by Access, does not enforce referential integrity by default. To enforce referential integrity, you must edit the relationship. See the section Change a table relationship for more information. Open a table in Datasheet view On the File tab, click Open. In the Open dialog box, select and open the database. In the Navigation Pane, right-click the table to which you want to add the field and create the relationship, and then click Open.
The Field List pane appears. The Field List pane shows all of the other tables in your database, grouped into categories. When you work with a table in Datasheet view, Access displays fields in either of two categories in the Field List pane: Fields available in related tables and Fields available in other tables.
The first category lists all of the tables that have a relationship with the table you are currently working with. The second category lists all of the tables with which your table does not have a relationship. To add a field to your table, drag the field that you want from the Field List pane to the table in Datasheet view.
Drag the field that you want from the Field List pane to the table that is open in Datasheet view. When the insertion line appears, drop the field in position. The Lookup Wizard starts.
Follow the instructions to complete the Lookup Wizard. The field appears in the table in Datasheet view. When you drag a field from an "other" unrelated table and then complete the Lookup Wizard, a new one-to-many relationship is automatically created between the table in the Field List and the table to which you dragged the field. Top of Page Delete a table relationship To remove a table relationship, you must delete the relationship line in the Relationships window.
Carefully position the cursor so that it points at the relationship line, and then click the line. The relationship line appears thicker when it is selected.
Note that when you remove a relationship, you also remove referential integrity support for that relationship, if it is enabled. As a result, Access will no longer automatically prevent the creation of orphan records on the "many" side of a relationship.
The Relationships window appears. If you have not yet defined any relationships and this is the first time you are opening the Relationships window, the Show Table dialog box appears. If the dialog box appears, click Close. All tables that have relationships are displayed, showing relationship lines. Click the relationship line for the relationship that you want to delete. Access might display the message Are you sure you want to permanently delete the selected relationship from your database?.
If this confirmation message appears, click Yes. If either of the tables employed in the table relationship are in use, perhaps by another person or process, or in an open database object such as a formyou will not be able to delete the relationship.
- relational database
- Many-to-many relationships
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You must first close any open objects that use these tables before you can remove the relationship. Top of Page Change a table relationship You change a table relationship by selecting it in the Relationships window and then editing it. Carefully position the cursor so that it points at the relationship line, and then click the line to select it.
With the relationship line selected, double-click it or click Edit Relationships in the Tools group on the Design tab. Click the relationship line for the relationship that you want to change.
Define a Many-to-Many Relationship and Many-to-Many Relationship Properties
Double-click the relationship line. Make your changes, and then click OK. The Edit Relationships dialog box allows you to change a table relationship. Specifically, you can change the tables or queries on either side of the relationship, or the fields on either side. You can also set the join type, or enforce referential integrity and choose a cascade option.
For more information about the join type and how to set it, see the section Set the join type.
For more information about how to enforce referential integrity and choose a cascade option, see the section Enforce referential integrity. Set the join type When you define a table relationship, the facts about the relationship inform your query designs.
For example, if you define a relationship between two tables, and you then create a query that employs those tables, Access automatically selects the default matching fields based upon the fields specified in the relationship. You can override these initial default values in your query, but the values supplied by the relationship will often prove to be the correct ones. Because matching and bringing together data from more than one table is something you will do frequently in all but the most simple databases, setting defaults by creating relationships can be time saving and beneficial.
A multiple table query combines information from more than one table by matching the values in common fields. The operation that does the matching and combining is called a join. For example, suppose you want to display customer orders. The query result contains customer information and order information for only those rows where a corresponding match was found. One of the values you can specify for each relationship is the join type.
The join type tells Access which records to include in a query result. For example, consider again a query that joins the Customers table and the Orders table on the common fields that represent the Customer ID.
Using the default join type called an inner jointhe query returns only the Customer rows and the Order rows where the common fields also called the joined fields are equal. To accomplish this, you must change the join type from an inner join to what is called a left outer join.
A left outer join returns all of the rows from the table on the left side of the relationship and only those that match from the table on the right.
A right outer join returns all of the rows on the right and only those that match on the left. In this case, "left" and "right" refer to the position of the tables in the Edit Relationships dialog box, not the Relationships window.