Key types §

• super key
  • value(s) that can identify a row in a table
• candidate key
  • super key without unneccessairy attributes
• primary key
  • candidate key selected by DB admin as a unique identifier
  • max 1
• alternate key
  • candidate keys which are not primary keys
• foreign key
  • primary key from another table
• composite key
  • candidate/primary key that consists of more than 1 attribute

Constraints §

= rules for data in a table (e.g. columns)

📖 Example: §

• primary/foreign key
• not null
• default (sets default value)
• check (checks if condition met)
• create index

Best practices for planning §

• normalize data
• place constraints
• document it
• create indexes

Postgres §

• Definition
  • precision = total num of digits
  • scale = num of digits to right of ,