create table Area (
aname varchar(20) primary key,
area_type varchar check( area_type in('rural','urban'))
);

create table Person(
pnumber int Primary key,
pname varchar(20),
birthdate date,
income numeric(7,2),
aname varchar(20),
constraint fk foreign key(aname) references Area(aname) on delete cascade on update cascade
);
insert into Area values('Pune','urban');
insert into Area values('Satara','urban');
insert into Area values('Mumbai','urban');
insert into Area values('Washim','rural');
insert into Area values('Khed','rural');


insert into Person values(101,'Raj Hawaldar','08/24/1995',50000.00,'Pune');
insert into Person values(102,'Sanket Dewale','07/12/1996',20000.00,'Khed');
insert into Person values(103,'Mandar Athavle','05/02/1996',30000.00,'Washim');
insert into Person values(104,'Nilesh Bora','08/20/1995',40000,'Mumbai');
insert into Person values(105,'Prathmesh Gurav','08/12/1995',10000,'Satara');
insert into Person values(106,'Ram Sultan','05/02/1993',30000,'Pune');
insert into Person values(107,'Kiran Shinde','1/08/1994',40000,'Mumbai');

select * from Person;

select * from Area;
select * from Person where aname='Pune';
select pname,income from Person where income<10000 ;
select pname from Person where area_type='urban' and income(max);

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;