Curso de Access | Capítulo 5 | Tablas Relacionadas en Access

Access allows powerful information management by relating data without complex procedures. This video will teach how to create relationships between tables and understand the importance of primary keys. A primary key is a special field in each table that uniquely identifies each record. For instance, an 'ID client' field ensures unique records, preventing duplicates and requiring a value for every entry. If a duplicate or blank value is entered, Access will show an error message.

By default, Access assigns the first field of a table as the primary key. To assign a different field, enter the table's design view, select the desired field, and click the 'Primary Key' icon. A small key icon will appear next to the field name, indicating it's the primary key. A table can only have one primary key. To change it, simply assign a new primary key, and the old one will be automatically removed. To remove a primary key, select the field in design view and deactivate the 'Primary Key' button.

Relationships in Access allow quick access to stored information without opening each table individually. This involves linking two tables through a common field. For example, relating customer data with sales data using a common 'ID client' field. It's crucial that the fields being related have the same data type. There are three types of relationships: 'one-to-many' where one record in a field can have multiple records in another table (e.g., one customer, many sales); 'many-to-many' where multiple records in one table can relate to multiple in another; and 'one-to-one' where each record in one table corresponds to only one record in another.

To create relationships, open the desired database, go to the 'Database Tools' tab, and click the 'Relationships' button. In the 'Show Table' dialog box, select the tables to relate and click 'Add', then 'Close'. Drag the common field from one table to the corresponding field in the other table. A 'Edit Relationships' dialog box will appear. Verify that the correct fields are selected, or modify them using the dropdown lists, then click 'Create'. A line will connect the two tables, indicating the successful relationship. Save the relationship. Now, when opening a related table, information from the other linked table will be visible.

Table relationships enable rapid information retrieval and creation of precise reports. The next chapter will cover important options regarding data integrity when working with related tables.