Two important steps for Database Design are :

1. Finding entities and relationships between them
2. Finding business rules that define how data will be stored

Consider below business statement :

Customer places orders to buy products

Entities are nouns. So , we can find entities in above business statement are all bold items i.e. Customer , Order and Product.

Entities may map to one table or may be to more tables.

Second aspect is business rule. Business rules example :

Applicant minimum age should be 18 years.
Credit Card no should be 16 digits.

So , one can define data integrity rules in database ( e.g. age should 18 and Credit card no should be 16 digits )

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