PostGres SQL Presented by : Chandan, Markandey Amit, Kiran Harshada, Prachi

Introduction What is ‘ PostGres ‘ ? An overview on Classes Inferitance Arrays Geometric Types

Inheritance A class can inherit from zero or more other classes. A query can reference to either all instances of a class or all instances of a class plus all of its descendents. The inheritance hierarchy is a directed acyclic graph.

Inheritance ( Cont. ) CREATE TABLE cities ( name text, population int, altitude int ) ; CREATE TABLE capitals ( state char10 ) INHERITS ( cities ) ;

Arrays Valid for variable-length & fixed-length multi-dimensional arrays. Array with n elements start by array[1] and ends with array[n]. CREATE TABLE sal_emp ( name text, pay int4[ ], schedule text[ ][ ] ) ;

Geometric Types Represent two dimensional spatial object. Points, Circle, Infinite Line, Rectangular Box etc. PostGres geometric type : ( x, y ) Point in Space ( (x1,y1), (x2,y2)) Line Circle

CreateUser Name : createuser - Create a new postgres user Synopsis : createuser [ options] [username] Inputs : - h : host. Host specifies the hostname of machine on which postmaster is running.

CreateUser ( Cont. ) - e : echo. Echo the queries that createdb generates and sends to the backend. username : Specifies the name of the postgres user to be created.This name must be unique among all postgres users.

CreateUser ( Cont.) Outputs : CREATE USER All is well createuser : creation of user “username” failed. Something went wrong. The user was not created.

CreateUser ( Cont. ) Description : createuser creates a new PostGres user. Only users with usesuper set in the pg_shadow class can create new PostGres users.

CreateUser ( Cont. ) Usage : To create user joe on the default database server. $ createuser joe Is the new user allowed to create databases? n CREATE USER

DropUser Name : dropuser - Drops (removes) a postgres user. Synopsis : dropuser [ options] [username] Inputs : - h : host.Host specifies the host name of machine on which postmaster is running.

DropUser ( Cont. ) - e : echo. Echo the queries that createdb generates and sends to the backend. Username : Specifies the name of the postgres user to be removed. This name must exist in the postgres installation.

DropUser ( Cont. ) Output : DROP USER All is well. Dropuser : deletion of user “username” failed. Something went wrong. The user was not removed.

DropUser ( Cont. ) Description : dropuser removes an existing user and the databases which that user owned. Only users with usesuper set in the pg_shadow class can destroy postgres users.

DropUser ( Cont. ) Usage : to remove user joe from the default database server. $ dropuser joe DROP USER

Applications Createdb - Create a new PostGres database. Destroydb - Remove an existing PostGres database. Createlang : Add a new programming language to a postgres database. Droplang : Remove a programming language from a postgres database.

Pg_Dump Name : pg_dump - Extract a PostGres database into a script file. Synopsis : pg_dump [options] [dbname]

Cont. Inputs : dbname : Specifies the name of the database to be extracted. Dbname defaults to the value of the USER environment variable. -a : Dump out only the data, no schema. -c : Clean schema prior to create

Cont. Output pg_dump will create a file or write to stdout Description pg_dump is a utility for dumping out a postgres database into a script file containing query commands.

Cont. The script files are in text format and can be used to reconstruct database,even on other machine and other architecture.pg_dump will produce the queries necessary to regenerate all user defined types,functions,tables,indices,aggregates and operators.

Cont. Usage To dump a database of the same name as the user: $pg_dump > db.out To reload this database: $psql -e database < db.out