Antipattern: Use a Generic Attribute Table

The solution that appeals to some programmers when they need to support variable attributes is to create a second table, storing attributes as rows. See the diagram below showing the two tables.

Each row in this attribute table has three columns:

• The Entity: Typically this is a foreign key to a parent table that has one row per entity.

• The Attribute: This is simply the name of a column in a conventional table, but we have to identify the attribute on each given row.

• The Value: Each entity has a value for each of its attributes.

For example, a given bug is an entity we identify by its primary key value 1234. It has an attribute called status. The value of that attribute for ...