Instances and Schemas Similar to types and variables in programming languages Logical Schema-the overall logical structure of the database Example:The database consists of information about a set of customers and accounts in a bank and the relationship between them Analogous to type information of a variable in a program Physical schema-the overall physical structure of the database Instance-the actual content of the database at a particular point in time Analogous to the value of a variable Database System Concepts-7th Edition 1.15 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 1.15 ©Silberschatz, Korth and Sudarshan th Edition Instances and Schemas ▪ Similar to types and variables in programming languages ▪ Logical Schema – the overall logical structure of the database • Example: The database consists of information about a set of customers and accounts in a bank and the relationship between them ▪ Analogous to type information of a variable in a program ▪ Physical schema – the overall physical structure of the database ▪ Instance – the actual content of the database at a particular point in time • Analogous to the value of a variable