Microsoft Access Tutorial (Part 2): Design View, Field Properties, & Relationships | n3ws.info
Learn how to create a relational database using Access including how to create and The instructions which follow use Access but they'll work pretty much the To create the relationship choose DataBase Tools > Relationships. To order the list so the query results appear in order by the date of the visit, click the . Learn how to create a relationship between tables with this Microsoft Access tutorial. This lesson teaches you how to sort and filter an Microsoft Access table. sorting , you can put a column of information in alphabetical, numerical, or date order.
The primary key of the junction table consists of the foreign keys from both table A and table B. For example, the "Authors" table and the "Titles" table have a many-to-many relationship that is defined by a one-to-many relationship from each of these tables to the "TitleAuthors" table.
One-to-one relationships In a one-to-one relationship, a row in table A can have no more than one matching row in table B, and vice versa. A one-to-one relationship is created if both of the related columns are primary keys or have unique constraints. This kind of relationship is not common, because most information that is related in this manner would be in one table. You might use a one-to-one relationship to take the following actions: Divide a table with many columns.
Isolate part of a table for security reasons. Store data that is short-lived and could be easily deleted by deleting the table. Store information that applies only to a subset of the main table. In Access, the primary key side of a one-to-one relationship is denoted by a key symbol. The foreign key side is also denoted by a key symbol. How to define relationships between tables When you create a relationship between tables, the related fields do not have to have the same names. However, related fields must have the same data type unless the primary key field is an AutoNumber field.
You can match an AutoNumber field with a Number field only if the FieldSize property of both of the matching fields is the same.
Even when both matching fields are Number fields, they must have the same FieldSize property setting. How to define a one-to-many or one-to-one relationship To create a one-to-many or a one-to-one relationship, follow these steps: You cannot create or change relationships between open tables. In Access or Accessfollow these steps: Press F11 to switch to the Database window. On the Tools menu, click Relationships. If you have not yet defined any relationships in your database, the Show Table dialog box is automatically displayed.
To create a relationship between a table and itself, add that table two times. Drag the field that you want to relate from one table to the related field in the other table. To drag multiple fields, press Ctrl, click each field, and then drag them.
In most cases, you drag the primary key field this field is displayed in bold text from one table to a similar field this field frequently has the same name that is called the foreign key in the other table. Make sure that the field names that are displayed in the two columns are correct. You can change the names if it is necessary. Set the relationship options if it is necessary. These options will be explained in detail later in this article.
Click Create to create the relationship. Repeat steps 4 through 7 for each pair of tables that you want to relate. Whether you save the layout or do not save the layout, the relationships that you create are saved in the database.
However, referential integrity is not enforced with queries. Totals and calculations in queries You can total results of a query. For example you can total all the amounts spent by each customer for the month of September. To do this, create a new query using the same process as detailed above this time containing just the fields FirstName and LastName from the Customer table and the AmountSpent field from the Visits table.
Now run this query. You can see that you have almost all the information you need, you just need a way to limit the data to visits that took place in September. To add this function to your query, return to the query design view and add the field DateOfVisit as the fourth column of your query note that the order of the field names in the columns is critical. Disable the Show checkbox for the field DateOfVisit as you don't want the data displayed on the screen.
From the Group By dropdown list for this field, choose the option Where and in the Criteria area for the DateOfVisit field type this line: Now run the query.
The result of the query will appear on the screen showing each customer and the amount in total that they spent for the month of September. Note that rather than asking the query to extract the data for September you have asked it to ask you which dates to use every time you run the query.
It's a good idea to create queries like this that can be used over and over again without needing to be altered. This sort of query is also good for users who aren't familiar with Access - it lets them find information without having to write a custom query to do it. You can save this query for reuse by clicking its Close button, answer Yes to the prompt to save it and give it a name like 'Customer spending summary by user inputted date range' and click OK.
Creating a Form for a Relational Database To make it easy to enter data into a relational database you can create a form to handle the data entry. When prompted with "How do you want to view your data?
Guide to table relationships
Click the Form with subform s option and click Next. A table relationship is represented by a relationship line drawn between tables in the Relationships window. A relationship that does not enforce referential integrity appears as a thin line between the common fields supporting the relationship.
When you select the relationship by clicking its line, the line thickens to indicate it is selected. If you enforce referential integrity for this relationship, the line appears thicker at each end. When the Relationships window is active, you can select from the following commands on the ribbon: On the Design tab, in the Tools group: When you select a relationship line, you can click Edit Relationships to change the table relationship.
You can also double-click the relationship line. The report shows only the tables and relationships that are not hidden in the Relationships window. On the Design tab, in the Relationships group: Note that hidden tables tables for which the Hidden check box in the table's Properties dialog box is selected and their relationships will not be shown unless Show Hidden Objects is selected in the Navigation Options dialog box.
If you made any changes to the layout of the Relationships window, you are asked whether to save those changes. Top of Page Create a table relationship You can create a table relationship by using the Relationships window, or by dragging a field onto a datasheet from the Field List pane.
When you create a relationship between tables, the common fields are not required to have the same names, although it is often the case that they do. Rather, those fields must have the same data type. If the primary key field is an AutoNumber field, however, the foreign key field can be a Number field if the FieldSize property of both fields is the same. When both common fields are Number fields, they must have the same FieldSize property setting. Create a table relationship by using the Relationships window Click File, and then click Open.
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.
Sorting, Filtering, and Relationships
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.
How to define relationships between tables in an Access database
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.