Installation process

Download the (Oracle Database 21c Express Edition) or (Oracle Database 11g Express Edition) and install the software. Remember the password during the installation because this password is used for connecting the database account.

Open the SQL Plus. Write 'connect system' and use the password that you set in the installation process. Follow the below figure.

You can create a new user because we use the system(administrator) as a user. Then, we will give the new user all privileges to perform all SQL tasks. Follow the figure. Change the password of the admin(system)

connect / as sysdba
alter user system identified by [password]

Creating user and giving system privileges

create user shakib034 identified by shakib034;

Delete any user

DROP USER username;

Granting system privileges Here, we give all the privileges to the user.

grant all privileges to shakib034;

Reboke all the privileges from the user

revoke all privileges from user_name

We can give specific privileges to the user.

grant create session to shakib034;

Creating a role(Assigned system privileges)

create role cse2k15;
grant create table, create session to cse2k15;
grant cse2k15 to shakib034;

Revoking System Privileges

revoke create table from shakib034;

Set line size and page size

show pagesize
show linesize

set pagesize 100
set linesize 200

Database project demo

SCHEMA

ERD

Run the SQL command

You can run SQL script by using the SQL command line. Besides, you can write your SQL command in a txt file and save the txt file as a SQL extension. Then, type the below command in the SQL command line.

start C:\Users\andromeda\Desktop\file.sql

Oracle data types

number(Precision,Scale)

Precision: total number of digits on either side of the decimal point

Scale: number of digits to the right of the decimal point

char vs varchar2 (varchar2: Variable-length character strings and char: Fixed-length character data)

Date format: DD-MON-YY

create table test(
name varchar2(30),
name2 char(3),
roll number(3),
GPA number(3,2),
roll2 number,
s_dob DATE
);

Here is a link about the oracle data types.

Checking current user name

show user

Checking the existing table in database.

select table_name from user_tables;

It shows that we already have two tables in my database. So we need to drop those tables from the database for a fresh start. You can use this command to drop any table.

drop table department;
drop table course;

First, we create the table "dept". Here, we can see that the primary key is dept_id because it uniquely identifies each row in the table.

Create table dept(
dept_id number(20),
dept_name varchar(30),
faculty varchar(30),
no_of_student number(20),
primary key(dept_id)
);

To see the last/immediate created table.

describe dept

We also create a course, book and relation table.

Create table course(
course_no varchar(20),
course_name varchar(50),
year_semister number(3),
credit number(20,4),
dept_id number(20),
primary key(course_no),
foreign key(dept_id) references dept(dept_id)
);
create table book(
book_no number(20),
book_name varchar(50),
author varchar(50),
book_edition number(4),
course_offering number(6),
primary key(book_no) 
);
create table relation(
book_no number(20),
course_no varchar(20),
primary key(book_no,course_no),
foreign key (book_no) references book(book_no),
foreign key (course_no) references course(course_no) 
);

When you observe the course table, they have another foreign key keyword referencing the dept_id from the "dept" table. We insert something in the course table. We must check whether this dept_id exists in the "dept" table.

DDL

Add column in the table

We add a column in the dept table which is location.

Command structure: alter table table_name add column_name column_definition;

alter table dept add location char(20);

Modify column definition in the table

Command structure: alter table table_name modify column_name column_definition;

We modify the location data types char(20) to varchar(23);

alter table dept modify location varchar(23);

Rename the column name

Command structure: alter table table_name rename column_name to column_name;

alter table dept rename column location to location2;

Drop the column from table

Command structure: alter table table_name drop column column_name;

alter table dept drop column location2;

DML

Insert the data in our table

insert into dept(dept_id,dept_name,faculty,no_of_student)values(7,'CSE','EE',120);

Here, "dept" refers to the table name, and we also insert values according to table columns. We also insert values into the other tables.

Insert the data in the table

insert into dept(dept_id,dept_name,faculty,no_of_student)values(3,'EEE','EE',120);
insert into dept(dept_id,dept_name,faculty,no_of_student)values(1,'CE','CE',120);
insert into dept(dept_id,dept_name,faculty,no_of_student)values(5,'ME','ME',120);
insert into dept(dept_id,dept_name,faculty,no_of_student)values(2,'ECE','EE',60);

insert into course(course_no,course_name,year_semister,credit,dept_id)values('CSE1101','discreate math',11,3.00,7);
insert into course(course_no,course_name,year_semister,credit,dept_id)values('CSE3105','database systems',31,3.00,7);
insert into course(course_no,course_name,year_semister,credit,dept_id)values('EEE1101','Basic electrical engineering',11,3.00,3);
insert into course(course_no,course_name,year_semister,credit,dept_id)values('ME3101','solid mechanics',31,3.00,5);

insert into book(book_no,book_name,author,book_edition,course_offering)values(12,'discreate math','rosen',4,2);
insert into book(book_no,book_name,author,book_edition,course_offering)values(13,'database systems','korth',5,1);
insert into book(book_no,book_name,author,book_edition,course_offering)values(14,'data_communication','willim stallings',6,3);
insert into book(book_no,book_name,author,book_edition,course_offering)values(15,'solid mechanics','john abraham',3,2);
insert into book(book_no,book_name,author,book_edition,course_offering)values(16,'electrical engineering','boylsted',8,4);

insert into relation(book_no,course_no)values(12,'CSE1101');
insert into relation(book_no,course_no)values(16,'EEE1101');
insert into relation(book_no,course_no)values(15,'ME3101');
insert into relation(book_no,course_no)values(13,'CSE3105');

All the data are inserted. Now, we do some experiments here. We run the command below.

insert into course(course_no,course_name,year_semister,credit,dept_id)values('MME1101','Basic structure of materials',11,3.00,9);

We inserted the course_no "MME1101" and course_id "9" in the course table. After running the command, we found this error. The course table refers to the dept table, and course id "9" does not exist in the dept table. So, it shows this error.

Displaying table data using SELECT command

Now, we find the rows from the "dept" table, which have 120 students using the select command.

select * from dept where no_of_student=120;

We find the dept_name, which course name is "database systems".

select * from dept where dept_id=(select dept_id from course where course_name='database systems');

Here, we add extra select command by adding an additional condition to find the dept_id in the "dept" table. This type of query is called a subquery.

Updating the data in a table

Now we want to update the value of the course name from the course table where course_no is "EEE1101"; Command structure: update table_name set column_name=value where condition;

update course set course_name='Digital Electronics' where course_no='EEE1101';

Deleting row from a table

We add an extra row to perform the delete operation in the dept table.

insert into dept(dept_id,dept_name,faculty,no_of_student)values(12,'URP','CE',60);

Now we delete the row from the dept table where dept_id is 12.

Command structure: delete from table_name where condition;

delete from  dept where dept_id=12;

union, intersect, and except

select dept_name from dept where dept_name like 'E%' union select dept_name from dept where dept_name like '%M%';

With clause

Calculates the maximum value of the no_of_student column from the dept table. The result of this subquery is a single row with a single column (val) containing the maximum value.

with max_student(val) as (select max(no_of_student) from dept)
select * from dept,max_student where dept.no_of_student=max_student.val;

Save the SQL command output

Save the SQL command output in CSV file

Simply change the folder path and your sql command.

SET COLSEP ","
SET HEADING OFF
SET PAGESIZE 0
SET FEEDBACK OFF
SPOOL C:\Users\andromeda\Desktop\file.csv
SELECT *
FROM dept;
SPOOL OFF

Save the SQL command output in txt file

Simply change the folder path and your sql command.

SPOOL C:\Users\andromeda\Desktop\file.txt
SELECT *
FROM dept;
SPOOL OFF

Aggregate function

We count how many row exist in dept table.

select count(*) from dept;

We also give alias name to any output in select command.

select count(dept_name) as number_of_dept from dept;

We can count distinct department name in dept table.

select count(distinct dept_name) as number_of_dept from dept;

We can count average and total no. of students in dept table.

select avg(no_of_student) from dept;
select sum(no_of_student) from dept;

We can find max and min no. of students of any department from dept table.

select max(no_of_student) from dept;
select min(no_of_student) from dept;

Group by and Having

Find the average of student according to faculty.

select faculty,avg(no_of_student) from dept group by faculty;

Find the average of student according to faculty where average of student is greater than 60.

select faculty,avg(no_of_student) from dept group by faculty having avg(no_of_student)>60;

Nested subquery

Find the department name where the “rosen”(author) book is taught.

 select dept_name from dept where dept_id=(select dept_id from course where course_no=(select course_no from relation where book_no=(select book_no from book where author='rosen')));

Set Membership(AND, OR,NOT)

Find the rows where faculty is "EE" and "CSE" string exists in course_no.

select * from dept where faculty='EE' and dept_id in (select dept_id from course where course_no like '%CSE%')

some/all/exists/unique

select * from book where book_no> some(select book_no from book where book_no>=14);
select * from book where book_no> all(select book_no from book where book_no>=14);

The exists construct returns the value true if the argument subquery is nonempty.

select * from course where year_semister>=11 and exists(select * from dept where faculty like '%EE%');

String operations

percent ( % ). The % character matches any substring.

underscore ( _ ). The _ character matches any character.

Demo table.

'E%' matches any string beginning with “E”.

SELECT * FROM TEST WHERE NAME LIKE 'E%';

'%E' matches any string ending with “E”.

SELECT * FROM TEST WHERE NAME LIKE '%E';

'%E%E%' contains with 'EE'.

SELECT * FROM TEST WHERE NAME LIKE '%E%E%';

'_ _ _' matches any string of exactly three characters.

SELECT * FROM TEST WHERE NAME LIKE '___';

Below command matches any string of at least three characters and at most five characters.

SELECT * FROM TEST WHERE NAME LIKE '___' or NAME LIKE '____' or NAME LIKE '_____';

Join operations

select * from dept natural join course where dept_id=7;

select * from dept natural join course;

select dept_name,course_name from dept join course using(dept_id);
select dept_name,course_name from dept join course on dept.dept_id=course.dept_id;

select dept_name,course_name from dept left outer join course using(dept_id);
select dept_name,course_name from dept right outer join course using(dept_id);
select dept_name,course_name from dept full outer join course using(dept_id);
select dept_name,course_name from dept left outer join course on dept.dept_id=course.dept_id;

Views

View definition is not the same as creating a new relation by evaluating the query expression.

A view of dept without their faculty,no_of_student.

create view dept_details as select dept_id,dept_name from dept;

Find all course in the CSE department.

create view CSE_DEPT_COURSE as select course_name from course where dept_id=(select dept_id from dept where dept_name='CSE');

Views Defined Using Other Views

create view  custom as select * from dept_details where dept_id>=3;

Cascading Actions in Referential Integrity

Create table dept2(
dept_id number(20),
dept_name varchar(30),
faculty varchar(30),
no_of_student number(20),
primary key(dept_id)
);
Create table course2(
course_no varchar(20),
course_name varchar(50),
year_semister number(3),
credit number(20,4),
dept_id number(20),
primary key(course_no),
foreign key(dept_id) references dept2(dept_id)
on delete cascade
);
insert into dept2(dept_id,dept_name,faculty,no_of_student)values(7,'CSE','EE',120);
insert into dept2(dept_id,dept_name,faculty,no_of_student)values(3,'EEE','EE',120);
insert into dept2(dept_id,dept_name,faculty,no_of_student)values(1,'CE','CE',120);
insert into dept2(dept_id,dept_name,faculty,no_of_student)values(5,'ME','ME',120);
insert into dept2(dept_id,dept_name,faculty,no_of_student)values(2,'ECE','EE',60);

insert into course2(course_no,course_name,year_semister,credit,dept_id)values('CSE1101','discreate math',11,3.00,7);
insert into course2(course_no,course_name,year_semister,credit,dept_id)values('CSE3105','database systems',31,3.00,7);
insert into course2(course_no,course_name,year_semister,credit,dept_id)values('EEE1101','Basic electrical engineering',11,3.00,3);
insert into course2(course_no,course_name,year_semister,credit,dept_id)values('ME3101','solid mechanics',31,3.00,5);

delete from dept2 where dept_id=5;

Constraints on a Single Relation

CREATE TABLE my_table (
    id INTEGER PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE NOT NULL,
    age INTEGER CHECK (age >= 18)
);
CREATE TABLE my_table2 (
    id INTEGER PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE NOT NULL,
    age INTEGER CHECK (age >= 18 AND age <= 120),
    status VARCHAR(10) CHECK (status IN ('active', 'inactive', 'pending')),
    start_date DATE NOT NULL,
    end_date DATE NOT NULL,
    CONSTRAINT check_age_status CHECK (
        (status = 'active' AND age >= 18 AND age <= 65) OR
        (status = 'inactive' AND age >= 18 AND age <= 120) OR
        (status = 'pending' AND age >= 18 AND age <= 100) OR
        (end_date > start_date)
    )
);

Insert data

insert into my_table values(1,'ss','ss@gmail.com',25);
insert into my_table2 values(3,'ss','ss@gmail.com',25,'active','03-APR-2007','04-APR-2009');

PL/SQL

Toad for oracle download

Download the (Toad) and install the software.

PL/SQL variable declaration and print value

set serveroutput on
declare 
dept_id dept.dept_id%type;
dept_name DEPT.DEPT_NAME%type;
no_of_student number;
begin
select dept_id,dept_name,no_of_student into dept_id,dept_name,no_of_student from dept where dept_id=7;
dbms_output.put_line('DEPT_id: '||dept_id|| ' DEPT_name: '||dept_name || ' no_of_student: '||no_of_student);
end;
/

Insert and set default value

set serveroutput on
declare 
dept_id dept.dept_id%type:=9;
dept_name DEPT.DEPT_NAME%type:='MME';
faculty dept.faculty%type:='ME';
no_of_student number:=30;
begin
insert into dept values(dept_id,dept_name,faculty,no_of_student);
end;
/

Row type

set serveroutput on
declare 
dept_row dept%rowtype;
begin
select dept_id,dept_name,no_of_student into dept_row.dept_id,dept_row.dept_name,dept_row.no_of_student from dept where dept_id=7;
end;
/

Cursor and row count

set serveroutput on
declare 
cursor dept_cursor is select * from dept;
dept_row dept%rowtype;
begin
open dept_cursor;
fetch dept_cursor into dept_row.dept_id,dept_row.dept_name,dept_row.faculty,dept_row.no_of_student;
while dept_cursor%found loop
dbms_output.put_line('DEPT_id: '||dept_row.dept_id|| ' DEPT_name: '||dept_row.dept_name || ' faculty: ' ||dept_row.faculty|| ' no_of_student: '||dept_row.no_of_student);
dbms_output.put_line('Row count: '|| dept_cursor%rowcount);
fetch dept_cursor into dept_row.dept_id,dept_row.dept_name,dept_row.faculty,dept_row.no_of_student;
end loop;
close dept_cursor;
end;
/

FOR LOOP/WHILE LOOP/ARRAY with extend() function

TYPE NAMEARRAY IS VARRAY(5) OF book.book_name%type;

It defines a user-defined collection type named NAMEARRAY as a variable array of 5 elements, with each element being of the same data type as the book_name column in the book table.

A_NAME NAMEARRAY:=NAMEARRAY();

It initializes a variable A_NAME of type NAMEARRAY.

set serveroutput on
declare 
  counter number;
  book_name2 book.book_name%type;
  TYPE NAMEARRAY IS VARRAY(5) OF book.book_name%type; 
  A_NAME NAMEARRAY:=NAMEARRAY();
begin
  counter:=1;
  for x in 12..16  
  loop
    select book_name into book_name2 from book where book_no=x;
    A_NAME.EXTEND();
    A_NAME(counter):=book_name2;
    counter:=counter+1;
  end loop;
  counter:=1;
  WHILE counter<=A_NAME.COUNT 
    LOOP 
    DBMS_OUTPUT.PUT_LINE(A_NAME(counter)); 
    counter:=counter+1;
  END LOOP;
end;
/

ARRAY without extend() function

DECLARE 
   counter NUMBER := 1;
   book_name2 book.book_name%TYPE;
   TYPE NAMEARRAY IS VARRAY(5) OF book.book_name%TYPE;
   A_NAME NAMEARRAY:=NAMEARRAY('Book 1', 'Book 2', 'Book 3', 'Book 4', 'Book 5'); 
   -- VARRAY with a fixed size of 5 elements and initialized with book names
BEGIN
   counter := 1;
   FOR x IN 12..16  
   LOOP
      SELECT book_name INTO book_name2 FROM book WHERE book_no=x;
      A_NAME(counter) := book_name2;
      counter := counter + 1;
   END LOOP;
   counter := 1;
   WHILE counter <= A_NAME.COUNT 
   LOOP 
      DBMS_OUTPUT.PUT_LINE(A_NAME(counter)); 
      counter := counter + 1;
   END LOOP;
END;

ARRAY with extend() and without extend() function

The A_NAME.EXTEND() method is used to dynamically increase the size of the varray A_NAME at runtime by one element. When you use A_NAME.EXTEND(), you don't need to know the size of the varray in advance, and you can add elements to the varray as needed.

On the other hand, if you declare the varray with a fixed size and initialize it with values at the beginning, you can assign values to the elements of the varray using the varray_name(index) := value syntax, as shown in the previous example. However, if you try to assign a value to an index that is beyond the fixed size of the varray, you will get a PLS-00302: component 'index' must be declared error.

So the main difference between using and not using A_NAME.EXTEND() is that with A_NAME.EXTEND(), you can dynamically resize the varray as needed, while without it, the varray has a fixed size and you cannot add more elements than the declared size.

IF /ELSEIF /ELSE

DECLARE 
   counter NUMBER := 1;
   book_name2 book.book_name%TYPE;
   TYPE NAMEARRAY IS VARRAY(5) OF book.book_name%TYPE;
   A_NAME NAMEARRAY:=NAMEARRAY('Book 1', 'Book 2', 'Book 3', 'Book 4', 'Book 5'); 
   -- VARRAY with a fixed size of 5 elements and initialized with book names
BEGIN
   counter := 1;
   FOR x IN 12..16  
   LOOP
      SELECT book_name INTO book_name2 FROM book WHERE book_no=x;
      if book_name2='discreate math' 
        then
        dbms_output.put_line(book_name2||' is a '||'CSE course');
      elsif book_name2='electrical engineering'  
        then
        dbms_output.put_line(book_name2||' is a '||'EEE course');
      else 
        dbms_output.put_line(book_name2||' is a '||'other dept course');
        end if;
   END LOOP;
END;

Procedure

CREATE OR REPLACE PROCEDURE proc2(
  var1 IN NUMBER,
  var2 OUT VARCHAR2,
  var3 IN OUT NUMBER
)
AS
  t_show CHAR(30);
BEGIN
  t_show := 'From procedure: ';
  SELECT course_name INTO var2 FROM course WHERE course_no IN (SELECT course_no FROM relation WHERE book_no = var1);
  var3 := var1 + 1; 
  DBMS_OUTPUT.PUT_LINE(t_show || var2 || ' code is ' || var1 || ' In out parameter: ' || var3);
END;
/

set serveroutput on
declare 
book_no book.book_no%type:=12;
course_name course.course_name%type;
extra number;
begin
proc2(book_no,course_name,extra);
end;
/

Function

set serveroutput on
create or replace function fun(var1 in varchar) return varchar AS
value dept.dept_name%type;
begin
  select dept_name into value from dept where dept_id=var1; 
   return value;
end;
/

set serveroutput on
declare 
value varchar(20);
begin
value:=fun(5);
end;
/

A function must return a value and procedure cannot return a value.

drop procedure and function

Stucture: drop procedure procedure_name Stucture: drop function function_name

drop procedure proc2;
drop function fun;

Trigger

Trigger body

create trigger [trigger_name] 
[before | after]  
{insert | update | delete}  
on [table_name]  
[for each row]  
[trigger_body] 

This trigger is named "try" and is set to execute before each row is deleted from the "relation" table The REFERENCING OLD AS o NEW AS n clause specifies that the trigger will reference the "old" values (i.e. the values before the deletion) as "o" and the "new" values (which do not exist in this case because it's a delete trigger) as "n".

Inside the trigger, there are two delete statements. The first statement deletes any rows from the "book" table where the "book_no" matches the value of "o.book_no" (i.e. the book number of the row being deleted from "relation"). The second statement deletes any rows from the "course" table where the "course_no" matches the value of "o.course_no" (i.e. the course number of the row being deleted from "relation").

SET SERVEROUTPUT ON
CREATE OR REPLACE TRIGGER try
BEFORE delete ON relation 
REFERENCING OLD AS o NEW AS n
FOR EACH ROW
BEGIN
delete from book where book_no=:o.book_no;
delete from course where course_no=:o.course_no;
END;
/

delete from relation where book_no=16;

The trigger is set to fire after an update operation is performed on the "course" table. For each row being updated, the trigger fires and updates the "book_name" column in the "book" table with the new course name (:n.course_name) where the "book_no" is present in the "relation" table for the corresponding old course number (:o.course_no).

SET SERVEROUTPUT ON
CREATE OR REPLACE TRIGGER trigger2
after update ON course 
REFERENCING OLD AS o NEW AS n
FOR EACH ROW
Enable
BEGIN
update book set book_name=:n.course_name where book_no in (select book_no from relation where course_no=:o.course_no);
END;
/

update course set course_name='discrete math2' where course_no='CSE1101';

This trigger is designed to execute after an insertion occurs in the "relation" table. It will update a related "book" table by incrementing the value of the "course_offering" field by 1, where the "book_no" matches the "book_no" of the newly inserted row.

The ":n.book_no" syntax refers to the "book_no" field in the newly inserted row (referenced as "n"). The "update" statement will modify the "book" table by incrementing the "course_offering" field by 1 for the row where the "book_no" matches the "book_no" of the newly inserted row.

SET SERVEROUTPUT ON
CREATE OR REPLACE TRIGGER trigger_new
after insert ON relation 
REFERENCING OLD AS o NEW AS n
FOR EACH ROW
Declare
bok integer;
BEGIN
update book set course_offering=course_offering+1 where book_no=:n.book_no;
END;
/

show errors;
select * from user_triggers;
drop trigger TRIGGER_NEW;

Reference

Silberschatz, A., Korth, H. F., & Sudarshan, S. (2023). Database System Concepts (7th ed.).