Specifying Metadata for DBMS Tables with Keys

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Tables in a database management system often have primary keys, unique keys, and foreign keys.

A primary key is one or more columns that are used to uniquely identify a row in a table. A table can have only one primary key. The column(s) in a primary key cannot contain null values.

A unique key is also one or more columns that can be used to uniquely identify a row in a table. A table can have one or more unique keys. Unlike a primary key, a unique key can contain null values.

A foreign key is one or more columns that are associated with a primary key or unique key in another table. A table might have one or more foreign keys. A foreign key is dependent upon its associated primary or unique key. In other words, a foreign key cannot exist without that primary or unique key.

Note

When specifying metadata for a DBMS table with foreign keys, if you want to preserve the foreign key, you must specify metadata for all of the tables that are referenced by the foreign keys.

For example, suppose that Table 1 had foreign keys that referenced primary keys in Table 2 and Table 3. To preserve the foreign keys in Table 1, you could use the Metadata Importer wizard or a source designer wizard to import metadata for Tables 1, 2, and 3.

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