PostgreSQL provides the utility program pg_dump to generate a text file with SQL commands that, when fed back to the server, will recreate the database in the same state as it was at the time of the dump.
pg_dump dbname > outfile
pg_dump can be used from the Linux console.
For example, if you want to backup a database called ‘my_database’ you run, from the console:
pg_dump my_database > my_database.sql
A data model is a collection of descriptions of the data and it’s relationships that hides details of the storage implementation. A database management system such as PostgreSQL or MS SQL allows users to define data models. The relational data model is a particular type of data model.
A more abstract data model is the semantic data model. It is usually used to develop an initial description of the data in a real world scenario, like a business or any other real world organization.
In the relational data model, a relation (table) can be thought as a set of records, like a table that contains information about employees in a company.
A record (row or tuple) represents a simgle item in a relation. Every row in the same relation has the same structure. For example, if, in the employees table, we can have a row that describes the employe named ‘Mike Smith’.
A field (column) represents a characteristic or variable of an entity described.