create table a(aid int primary key,aname text, type text check (type in('urban','rural')));
 create table p(pno int primary key,name text,birthdate date, income money,aid int references a(aid));
 
 insert into a values('12','aa','rural'),('11','bb','rural'),('13','cc','urban');
 insert into p values('1','rutu','09/09/2005','9000000','11'),('2','ruhi','09/08/2005','8000000','13'),
('3','rutuja','08/09/2005','7000000','12');
select * from a;
 select * from p;
 
create or replace function r()
 returns void as'
 begin
 update p set income=income+income*''0.10'' 
 where aid in(select aid from a where type=''rural'');
 end;
 'language plpgsql;
 select r();
 select * from p;
 
 
 create or replace function t()
 returns trigger as'
 begin
 raise notice''person record is being deleted'';
 return old;
 end;
 'language plpgsql;
 
 create trigger t
 before delete on p
 for each row execute 
 procedure t();
 
 delete from p where pno='1';
 select * from p;
 
 create or replace function n()
 returns text as'
 declare 
 r p.name%type;
 c cursor for select p.name from p,a where 
 p.aid=a.aid and a.type=''urban'';
 begin
 open c;
 loop
 fetch c into r;
 exit when not found;
 raise notice ''pname=% '',r;
 end loop;
 close c;
 end;
 'language plpgsql;
 select n();
by

PostgreSQL online editor

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About PostgreSQL

PostgreSQL is a open source relational database system and is also knows as Postgres.

Key Features:

  • Postgres is not only free and open-source but also it is highly extensible.
  • Custom Data types and funtions from various programming languaues can be introduced and the good part is compiling entire database is not required.
  • ACID(Atomicity, Consistency, Isolation, Durability) compliant.
  • First DBMS which implemented Multi-version concurrency control (MVCC) feature.
  • It's the default database server for MacOS.
  • It supports all major operating systems like Linux, Windows, OpenBSD,FreeBSD etc.

Syntax help

1. CREATE

CREATE command is used to create a table, schema or an index.

Syntax:

         CREATE TABLE table_name (
                column1 datatype,
                column2 datatype,
                ....);

2. ALTER

ALTER command is used to add, modify or delete columns or constraints from the database table.

Syntax

ALTER TABLE Table_name ADD column_name datatype;

3. TRUNCATE:

TRUNCATE command is used to delete the data present in the table but this will not delete the table.

Syntax

TRUNCATE table table_name;

4. DROP

DROP command is used to delete the table along with its data.

Syntax

DROP TABLE table_name;

5. RENAME

RENAME command is used to rename the table name.

Syntax

ALTER TABLE table_name1 RENAME to new_table_name1;

6. INSERT

INSERT Statement is used to insert new records into the database table.

Syntax

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

7. SELECT

Select statement is used to select data from database tables.

Syntax:

SELECT column1, column2, ...
FROM table_name;

8. UPDATE

UPDATE statement is used to modify the existing values of records present in the database table.

Syntax

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

9. DELETE

DELETE statement is used to delete the existing records present in the database table.

Syntax

DELETE FROM table_name where condition;