Queries_Class of DB

8/7/2019 Queries_Class of DB

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Create, Delete and UpdateCreate, Delete and UpdateLab 01Lab 01


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QUICK VIEW OF SQLSERVER 2005


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Data types inData types in

SQL PlusSQL Plus

char(n): Fixed-length character data (string), n characters long. Themaximum size for n 2000 in Oracle8. Example: char(40)

varchar 2(n): Variable-length character string. The maximum size for n is 4000in Oracle8. Example: varchar2(80).

number(o, d): Numeric data type for integers and reals. o = overall number ofdigits, d = number of digits to the right of the decimal point. Examples: number(8),number(5,2). Note that, e.g., number(5,2) cannot contain anything larger than999.99 without resulting in an error. Data types derived from number are int[eger],dec[imal], smallint and real.

date: Date data type for storing date and time. The default format for a date is: DD-MMM-YY. Examples:13-OCT-94, 07-JAN-98.

long: Character data up to a length of2GB.


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Using SQLUsing SQL

DESCRIBE ;DESCRIBE ;

DESCRIBE statement is used to display

the columns of a table and their data

types means the structure of table.


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Using SQLUsing SQL

COMMIT;COMMIT;

ROLLBACK;ROLLBACK;

A sequence of database modifications, i.e. insert,

update, and delete statements is called a

TRNASACTION. COMMIT makes permanent any

database changes you made during the currenttransaction. As long as the user has not issued the

commit statement, it is possible to undo all modifications

since the last commit. To undo modifications, one has to

issue the statement ROLLBACK.


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Using SQLUsing SQL

Select * from tab;Select * from tab;

TAB is a table in Oracle. TAB table

contains a list of all of the tables in a

database.


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Using SQLUsing SQL

To create a table in the current database,

use the CREATE TABLE keyword

create table ( [not null] [unique] [],

. . . . . . . . .

[not null] [unique] [],

[]

);

[constraint ] primary key | unique | not null


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ExampleExample

CREATE TABLE authorsCREATE TABLE authors

(auth_id int(9) not null,(auth_id int(9) not null,

auth_name char(40) not null)auth_name char(40) not null)

auth_id auth_name

(9 digit int) (40 char string)


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Using SQLUsing SQL

To insert data in the current table, use

the keyword INSERT INTO

INSERT INTO [()]

values ();


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ExampleExample

INSERT INTO authors

values(00001, John Smith)

INSERT INTO authors

values(00002, Jane Doe)

auth_id auth_name

00001 John Smith

00002 Jane Doe

Then issue the statement

SELECT * FROM authors


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Using SQLUsing SQL

If you want to enter 100 records then you can avoid to

write insert statement 100 times by making use of

substitution variable.

INSERT INTO company VALUES (&cname, &city) Youll set prompts for entering values of cname

and city.

Enter the value of cname:- GSK

Enter the value of city:- Karachi


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Using SQLUsing SQL

You enter the above values and press enter you

will get message

Record created.

If you want to insert another record in sametable just type RUN at SQL prompt as:

Run;


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Using SQLUsing SQL

DELETE from [whereDELETE from [where

];];

To delete data from a table, use

the DELETE statement:


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ExampleExample

auth_id auth_name

00002 Jane Doe

000000001 John Smith

DELETE from authorsDELETE from authors

WHERE auth_name=John SmithWHERE auth_name=John Smith


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Using SQLUsing SQL

UPDATE setUPDATE set

= , . . = , . .

. , = . , =

[where ];[where ];

To Update information in a database use

the UPDATE keyword


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ExampleExample

auth_id auth_name

00001 Hello

00002 Hello

UPDATE authorsUPDATE authors

SET auth_name=helloSET auth_name=hello

Sets all auth_name fields to helloSets all auth_name fields to hello


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Using SQLUsing SQL

ALTER TABLE ALTER TABLE

ADD( ADD(

[default ] []);

To change a table in a database use ALTER

TABLE. ADD adds a characteristic.


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ExampleExample

auth_id auth_name

00002 Jane Doe

00001 John Smith

ALTER TABLE authorsALTER TABLE authors

ADD birth_date datetime nullADD birth_date datetime null

ADD puts a new column in the table

called birth_date

birth_date

.

.

Type Initializer


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Using SQLUsing SQL

DROP TABLE [cascadeDROP TABLE [cascade

constraints];constraints];

The DROP command removes a table

from the database. All the tables' rows,

indexes and privileges will also beremoved


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ExampleExample

auth_id auth_name auth_city auth_state

123456789 Jane Doe Dearborn MI

000000001 John Smith Taylor MI

DROP TABLE authors;DROP TABLE authors;


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Using SQLUsing SQL

TRUNCATE TABLE ;TRUNCATE TABLE ;

The TRUNCATE command clears the

records from the table but the table

structure still remains. It can't roll back.


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Exercise

We want to create a table called PROJECT to store informationabout projects. For each project, we want to store the numberand the name of the project, the employee number of theprojects manager, the budget and the number of personsworking on the project, and the start date and end date of the

project. Furthermore, we have the following conditions: a project is identified by its project number,

the name of a project must be unique,

the manager and the budget must be defined.

no two projects have the same start and end date.

If no start date is given when inserting a tuple into the tablePROJECT, the project start date should be set to January 1st,2000.


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Table Definition

create table PROJECT (

PNO number(3) constraint prj_pk primary key,

PNAME varchar2(60) unique,

PMGR number(4) not null,

PERSONS number(5),

BUDGET number(8,2) not null,

PSTART date default(01-JAN-00),

PEND date,

constraint no_same_dates unique (PEND, PSTART) );


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INSERTION

insert into PROJECT(PNO, PNAME, PERSONS,BUDGET, PSTART)

values(313, DBS, 4, 150000.42, 10-OCT-94);

OR

insert into PROJECT

values(313, DBS, 7411, null, 150000.42, 10-OCT-94, null);


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Foreign key Constraintcreate table DEPARTMENT(

departt_id number(5) primary key,

departt_name varchar2(20) not null,

constraint departt unique(departt_name)

);

create table DESIGNATION(

desig_id number(5)primary key,

desig_name varchar2(20) not null,

constraint desig unique(desig_name)

);

create table VACANCY(

vac_id number(5) primary key,

vac_exp varchar2(20),

desig_id number(5) constraint fk_con references DESIGNATION(desig_id),

departt_id number(5) references DEPARTMENT

);


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Example 2CREATE TABLE supplier

( supplier_id numeric(10) not null,

supplier_name varchar(50) not null,

contact_name varchar(50),

CONSTRAINT supplier_pk PRIMARY KEY (supplier_id, supplier_name) );

CREATE TABLE products( product_id numeric(10) not null,

supplier_id numeric(10) not null,

supplier_name varchar(50) not null );

ALTER TABLE products

add CONSTRAINT fk_supplier

FOREIGN KEY (supplier_id, supplier_name)

REFERENCES supplier(supplier_id, supplier_name)

ON DELETE CASCADE

ON UPDATE cascade;


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INSERT INTO supplier VALUES (1,'Ali','Ali')

INSERT INTO supplier VALUES (2,'Sara','Sara')

INSERT INTO products VALUES (1,1,'Ali')

INSERT INTO products VALUES (2,2,'Sara')

update supplier set supplier_name='ABC' wheresupplier_name='Ali'

delete from supplier where supplier_name='ABC'

select * from products

select * from supplier


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Answer of Queries given in paper

1. select Distinct s.sname from student s, classc, Enrolled e where s.snum=E.snum and

e.cname=c.name and c.name=database' and

s.level = 'JR

OR

1. select distinct s.sname from student s,

enrolled e where s.level=JR' and

s.snum=e.snum and e.cname=database'

2. select s.level, avg(s.age) from student s

group by s.level

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Queries_Class of DB