Review Lecture

FLWR

• For
• Let
• Where
• Return

Mongo DB uses semi structured data, similar to XML

• Data is in JSON Format

Data Bases get used for many applications

• You cannot change its structure for the sake of one application, because it will cause others to break
• Incompatibilities: Two, similar databases will mismatch in some ways

Federation: Everybody talks directly to everyone else - Any Database interaction will go through a wrapper to ensure compatibility Warehouse: Sources are translated from their local schema to a global schema and copied to a central DB Mediator: a virtual warehouse allowing for distributed communication

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SQL Review

• The SELECT statement allows us to select data from one or more tables.