The entity relationship diagram has some limitations as to its use in extracting information from the database. It is useful for the analyst to see how data are related and to see the available attributes; however, it has the following limitations for the analyst writing SQL:
The names of the entities may not match the names of the tables.
The names of the attributes may not match the names of the table’s columns.
Foreign-key columns are not shown.
Database tables can be represented by relationships or as an attribute rather than as an entity. Examples are multivalued attributes and Many-to-Many relationships that may have associated attributes.
The best tool to use is the data schema ...