A true relational database must go beyond throwing data into a few tables and writing some SQL statements to pull that data out.
At best a badly designed table structure will slow the execution of queries and could make it impossible for the database to function as intended.
A database table should not be considered as just another table; it has to follow a set of rules to be considered truly relational. Academically it is referred to as a 'relation' to make the distinction.
The five rules of a relational table are:
A table conforming to the five rules:
Manageronly contain a single value.
Idcontains only integers,
Namecontains text (we could add that it's text of four characters or less),
DOBcontains dates of a valid type and
Managercontains integers (we could add that corresponds to a Primary Key field in a managers table).
Managerare unique heading names within the table.
Idfield ensures that each record is distinct from any other record within the table.
A badly designed table:
|3||Sue||Friday the 18th July 1975||2, 1|