A design tool that graphically expresses the database’s overall logical structure by representing data entities, their cardinality relationships (e.g., one-to-one, one-to-many, etc.), and the linkages that connect them. The construction of an ER diagram is essential for the design of database tables, extracts, and metadata (see definition of metadata). ER diagrams are especially important in designing and developing data documentation and tables that represent data relationships (see data/process flow diagram and data structure diagram).
