Database (Joining, Trigger & )

15-02-2019

It Is a collection of interrelated data

Data-it is unorganized ,unstructured , unmanaged fact & figure.

Information-It is organized, structured ,managed fact & figure. DBMS(Database Management System)

IT is a software package which is used to managed & Create database. Example:-dbase ,DB1,DB2, MS-acess oracle ,PostgreSQL, SQL –SERVER ,SQL lite Ingress etc. Type of DBMS based on model

• RDBMS-Ms Access, Oracle ,MYSql etc • Hierarchical DBMS • Network database Management System • Object-oriented Database management System. TYPE OF KEYS

• Super Keys-Group of attribute which are uniquely identify each record. • Primary key-Those attribute which are uniquely identify each record and does not store value. • Candidate keys-The minimal set of attribute which can uniquely identify each tuple. Each may have one or more candidate keys. But one is unique. And it is called the primary keys. • - It should be primary key of another table used to establish relationship between two and more tables. It based on . • Alternative keys- After selecting candidate keys, The rest keys is known as Alternative keys. SQL(Structured )

• DDL() • Create, Alter, Truncate , Drop, Rename

• DML(Data Manipulation Language) • Insert , Update, Select , Delete , move

• DCL() • Grant Revoke • TCL(transaction Control Language) Rollback Save point SQL query example

1.SELECT * FROM student WHERE S_ID=`100`;

2.SELECT * FROM student WHERE course=`BCA` AND city=``Delhi`;

3. 2.SELECT * FROM student WHERE course=`BCA` OR city=``Delhi`;

4.SELECT * FROM student ORDER BY course ASC,City DESC; SQL EXAMPLE

• INSERT INTO STUDENT • (S_ID, S_NAME,S_COURSE,S_PHN NO) • VALUES(`100`,`vikash``MBA``998765123`);

• UPDATE student • SET s_name=`vikash` • WHERE PHN NO=`987617717` ; SOME EXMPLE(using function)

• SELECT COUNT(S_ID) • FROM student ; Some example using LIKE operator

• SELECT *FROM student • WHERE S_name LIKE `%vk%`;

• SELECT * FROM STUDENT • WHERE CITY IN(`DELHI`.`PATNA`); Example of DDL

• CREATE TABLE Student (S_ID int NOT NULL, Name varchar(255) NOT NULL, Course varchar(200), NOT NULL);

• DROP table student;

• AlTER TABLE Student DROP DOB;

• It is a procedural language Which take instances of as input and give occurrence of relation as output .it uses various operation to perform this action

• Type of operator- • Select • Projection • Union • Set different • Cartesian product • Rename Type of relational operator

• SELECT (σ) • The SELECT operation is used for selecting a subset of the tuples according to a given selection condition. Sigma(σ)Symbol denotes it. • Example- • σsubject = "database"(Books)

• Output − Selects tuples from books subject is 'database' LEVEL OF DATA BASE SQL JOIN

• A JOIN clause is used to combine rows from two or more tables, based on a related column between them.

• different type of SQL JOINs • 1.INNER JOIN • 2.LEFT(OUTER) JOIN • 3.RIGHT(OUTER) JOIN • FULL(OUTER) JOIN INNER JOIN

• Return records that have matching value in both table • Syntax- • SELECT column_name(s) FROM table1 INNER JOIN table2 ON table1.column_name = table2.column_name; • LEFT(OUTER) JOIN

• The LEFT OUTER keywords returns all records from left table and the matches records from the right table. • Syntax- • SELECT column_name(s) FROM table1 LEFT JOIN table2 ON table1.column_name = table2.column_name;

• RIGHT(OUTER) JOIN

• RIGHT(OUTER) keywords returns all records from the right table and matched records from the left table. • Syntax- • SELECT column_name(s) FROM table1 RIGHT JOIN table2 ON table1.column_name = table2.column_name; FULL(OUTER) JOIN

The FULL OUTER JOIN keywords returns all records when there is matching in either left table or right table. Syntax- SELECT column_name(s) FROM table1 FULL OUTER JOIN table2 ON table1.column_name = table2.column_name; TRIGGER IN DBMS

• Trigger in DBMS is a special kind of procedural that automatically executed when an event(INSERT,UPDATE,DELETE) occurs in the database server.

• Trigger executes when a user tries to modify data through a DML event such as Insert, Delete, Update. Syntax of trigger

• CREATE or REPLACE TRIGGER display_marks_changes BEFORE DELETE OR INSERT OR UPDATE ON students For EACH WHEN(NEW.ID > 0) DECLARE Marks_diff number; BEGIN Marks_Diff:= :New. Marks - :Old. Marks; Dbms_output.put_line (`old Marks` : || :OLD. Marks); Dbms_output.put_line (`New Marks` : || :New. Marks); Dbms_output.put_line (`Marks difference` : || :Marks_diff); END; Cursor

• A cursor is a pointer to this context area • PL/SQL control context the through a cursor. • A cursor holds the rows return by a SQL Statement.

• Context area-Oracle Create a memory area as the context area, for processing an SQL statement which contains all the information needed for processing the statement: • example-no of rows processed etc. Type of cursor

• Implicit cursor • IT is automatically created by oracle whenever an SQL Statement is executed.

• Explicit Cursor • IT is a programmer-defined cursor for gaining more control over the context area. Cursor Action-----

• Declare - Cursor is declare by defining the SQL • Open- A cursor is opened and populated by executing the SQL • Fetch- When the cursor is opened rows can be fetched from the cursor one by one • Close- After data manipulation close the cursor • Deallocate- finally the cursor and release all the system

General syntax of cursor- CURSOR cursor_name IS Select _Statement.