INDEX

Sr. No.

Experiments Remark

1. Introduction to DBMS

2. To create a table, alter and drop table.

3. To perform select, update, insert and delete operation in a table

4. To make use of different clauses viz where, groupby, having, order by, union, intersection ,set difference

5. To study different constraints

6. To use SQL functions viz aggregate, numeric ,converison, string functions.

7. To understand use and working of joins

8. To understand use and working of sub - queries

9. To make use of transaction control statements viz rollback, commit and savepoint

10. To make views of a table

EXPERIMENT NO: 5

AIM: TO STUDY DIFFERENT CONSTRAINTS

THEORY:

CONSTRAINTS

CONSTRAINTS enforces RULES at the table level

Constraints prevent the deletion of the table if there is DEPENDENCIES from the other table. Basically, Constraints are used to PREVENT INVALID DATA ENTRIES INTO THE TABLES.

HOW TO DEFINE A CONSTRAINT:

SYNTAX:

SQL> CREATE TABLE [table name] (column datatype [Default expr] [column_constraint], …….. [table_constraint][,….]);

“ NOT NULL” : THE “NOT NULL” CONSTRAINT

This constraint ensures that the column contains no null values. As column without the NOT NULL constraint can contain NULL values BY DEFAULT.

Here, On table STUDENT NOT NULL constraint is added to the LAST_NAME i.e. now LAST_NAME can’t be NULL

If we try to add NULL value in this column then following message will be displayed as ERROR.

Whereas we can add NULL value to the NAME column as there exist no NOT NULL constraint.

PRIMARY KEY:

A PRIMARY KEY constraint creates a primary key for a table. Only one primary key can be created for each table.

A PRIMARY KEY constraint is a column or a set of columns that are uniquely identifies each row in the table.

This constraint enforces UNIQUENESS of the column or column combination and ensures that no column that is part of the primary key can contain a NULL value.

NULL VALUES are NOT ALLOWED & ALREADY existing values are not replaced.

In this Department_id is a PRIMARY KEY. i.e.

It do not contain DUPLICATE entries & NO NULL values.

If we try to add DUPICATE values than following ERROR is encountered.

If we try to add NULL value than following ERROR is encountered.

PRIMARY KEY constraint can be defined at the COLUMN LEVEL or TABLE LEVEL. A composite PRIMARY KEY is created by using the TABLE-LEVEL definition.

A table can have only one PRIMARY KEY constraint but can have several UNIQUE

constraints. We can call them ALTERNATE KEYS.

FOREIGN KEY:

The FOREIGN KEY, or refrential integrity constraint, designates a column or combination of columns as a foreign key and establishes a relationship between a primary key or a unique key in the same table or a different table.

A FOREIGN KEY value must match an existing value in the parent table or be NULL

FOREIGN KEYS are based on data values and are purely logical, not physical, pointers.

SYNTAX:

SQL> CREATE TABLE table2 (… department_id NUMBER(4) CONSTRAINT emp_deptid_fk REFERENCES table1(department_id), …)

The FOREIGN KEY is defined in the child table, and the table containing the referenced column is the Parent table. The FOREIGN KEY is defined using the combination of the following keywords:

FOREIGN KEY: is used to define the column in the child table at the table constraint level.

REFERENCES: identifies the table and column in the parent table.

ON DELETE CASCADE: indicates that when the row in the parent table is deleted, the dependent rows in the chile table will also be deleted.

ON DELETE SET NULL: converts foreign key values to the NULL when parent value is REMOVED.

Here, ‘5’ NOT ALLOWED value as ‘5’ doesn’t EXIT

CHECK Constraint

The CHECK constraint is used to limit the value range that can be placed in a column.

If you define a CHECK constraint on a single column it allows only certain values for this column.

If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row.

SQL CHECK Constraint on CREATE TABLE

The following SQL creates a CHECK constraint on the "P_Id" column when the "Persons" table is created. The CHECK constraint specifies that the column "P_Id" must only include integers greater than 0.

CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CHECK (P_Id>0) )

SQL CHECK Constraint on ALTER TABLE

To create a CHECK constraint on the "P_Id" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons ADD CHECK (P_Id>0)

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

ALTER TABLE Persons ADD CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')

To DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons DROP CONSTRAINT chk_Person

SQL UNIQUE Constraint

The UNIQUE constraint uniquely identifies each record in a database table.

The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns.

A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it.

Note that you can have many UNIQUE constraints per table, but only one PRIMARY KEY constraint per table.

SQL UNIQUE Constraint on CREATE TABLE

The following SQL creates a UNIQUE constraint on the "P_Id" column when the "Persons" table is created:

CREATE TABLE Persons ( P_Id int NOT NULL UNIQUE, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255) )

To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple columns, use the following SQL syntax:

CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName) )

SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "P_Id" column when the table is already created, use the following SQL:

ALTER TABLE Persons ADD UNIQUE (P_Id)

To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple columns, use the following SQL syntax:

ALTER TABLE Persons ADD CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)

To DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

ALTER TABLE Persons DROP CONSTRAINT uc_PersonID

EXPERIMENT NO: 6

AIM: TO USE FUNCTIONS VIZ AGGREGATE, NUMERIC ,CONVERISON, STRING FUNCTIONS.

THEORY: Aggregate Functions

COUNT : This function returns the number of rows or non-null values for column x.

SYNTAX

COUNT([DISTINCT|ALL]COLUMN NAME)

EXAMPLE

SQL>SELECT COUNT(EMPNO)FROM EMP;

SUM : This function ireturns the sum of values for the column x. This function is applied on columns having numeric datatype and it returns the numeric value.

SYNTAX

SUM([DISTINCT|ALL]COLUMN NAME)

EXAMPLE

SQL>SELECT SUM(SAL) FROM EMP;

AVG : Ths function returns the average of values for the column x. It ignores the null values in the column x.

SYNTAX

AVG([DISTINCT|ALL]COLUMN NAME)

EXAMPLE

SQL>SELECT AVG(SAL),COUNT(SAL) FROM EMP;

MIN : This function returns the minimum of values for the column x for all the rows.

SYNTAX

MIN([DISTINCT|ALL]COLUMN NAME)

EXAMPLE

SQL>SELECT MIN(SAL) FROM EMP;

MAX : This function returns the maximum of values for the column x for all the rows.

SYNTAX

MAX([DISTINCT|ALL]COLUMN NAME)

EXAMPLE

SQL>SELECT MIN(SAL),MAX(SAL) FROM EMP;

NUMERIC FUNCTIONS:Numeric functions are used to perform operations on numbers. They accept numeric values as input and return numeric values as output. Few of the Numeric functions are:

Function Name Return Value

ABS (x) Absolute value of the number 'x'

CEIL (x) Integer value that is Greater than or equal to the number 'x'

FLOOR (x) Integer value that is Less than or equal to the number 'x'

TRUNC (x, y) Truncates value of number 'x' up to 'y' decimal places

ROUND (x, y) Rounded off value of the number 'x' up to the number 'y' decimal places

The following examples explains the usage of the above numeric functions

Function Name Examples Return Value

ABS (x)ABS (1) ABS (-1)

1 -1

CEIL (x)CEIL (2.83) CEIL (2.49) CEIL (-1.6)

3 3 -1

FLOOR (x) FLOOR (2.83) 2

FLOOR (2.49) FLOOR (-1.6)

2 -2

TRUNC (x, y)ROUND (125.456, 1) ROUND (125.456, 0) ROUND (124.456, -1)

125.4 125 120

ROUND (x, y)

TRUNC (140.234, 2) TRUNC (-54, 1) TRUNC (5.7) TRUNC (142, -1)

140.23 54 5 140

These functions can be used on database columns.

ROUND FUNCTION:

SYNTAX:

SQL> SELECT ROUND(45.923, 2), ROUND(45.923,0),

ROUND(45.923,-1) FROM DUAL;

TRUNC FUNCTION:

SYNTAX:

SQL> SELECT TRUNC(45.923, 2), TRUNC(45.923,0),

TRUNC(45.923,-1) FROM DUAL;

MOD FUNCTION:

SYNTAX:

SQL> SELECT MOD(300,10), MOD(23,9) FROM DUAL;

SQL> SELECT ename, MOD(sal,200) FROM emp;

CONVERSION FUNCTIONS:These are functions that help us to convert a value in one form to another form. For Ex: a null value into an actual value, or a value from one datatype to another datatype like NVL, TO_CHAR, TO_NUMBER, TO_DATE.

Few of the conversion functions available in oracle are:

Function Name Return Value

TO_CHAR (x [,y])Converts Numeric and Date values to a character string value. It cannot be used for calculations since it is a string value.

TO_DATE (x [, Converts a valid Numeric and Character values to a Date value.

date_format]) Date is formatted to the format specified by 'date_format'.

NVL (x, y)If 'x' is NULL, replace it with 'y'. 'x' and 'y' must be of the same datatype.

DECODE (a, b, c, d, e, default_value)

Checks the value of 'a', if a = b, then returns 'c'. If a = d, then returns 'e'. Else, returns default_value.

The below table provides the examples for the above functions

Function Name Examples Return Value

TO_CHAR () TO_CHAR (3000, '$9999') TO_CHAR (SYSDATE, 'Day, Month YYYY')

$3000 Monday, June 2008

TO_DATE () TO_DATE ('01-Jun-08') 01-Jun-08NVL () NVL (null, 1) 1

STRING FUNCTIONS

UPPER FUNCTION:

SYNTAX:

SQL> SELECT UPPER(ename)||’ is a ’|| job AS “EMPLOYEE DETAILS” FROM emp;

LOWER FUNCTION

SYNTAX:

SQL> SELECT LOWER(ename) NAME, UPPER(job) JOB FROM emp WHERE sal>2000;

INITCAP FUNCTION:

SQL> SELECT INITCAP(ename) NAME, UPPER(job) JOB FROM emp WHERE sal>2000;

CONCAT FUNCTION

SYNTAX:

SQL> SELECT CONCAT(ename,sal) NAME FROM emp;

LENGTH FUNCTION

SYNTAX:

SQL> SELECT LENGTH(ename), sal FROM emp;

LPAD FUNCTION

SYNTAX:

SQL> SELECT LPAD(sal,8,’*’) FROM EMP;

RPAD FUNCTION:

SYNTAX:

SQL> SELECT RPAD(sal,8,’$’) FROM emp WHERE sal>3000;

SUBSTRING FUNCTION:

SYNTAX:

SQL> SELECT sal,job FROM emp WHERE SUBSTR(ename,-1,1)=’n’;

INSTRING FUNCTION:

SYNTAX:

SQL> SELECT ename,INSTR(ename,’A’), job FROM emp WHERE sal>2000;

EXPERIMENT NO: 7

AIM: TO UNDERSTAND USE AND WORKING OF JOINS

THEORY: JOINS

A JOIN can be recognized in sql select statement if its has more than one table after from keyword. This join condition is based on primary keys and foreign keys. There must be n-1 join conditions for n joins to tables. If join condition is omitted then the result is Cartesian product.

SYNTAX

SQL>SELECT “list of columns” FROM table1, table2 WHERE “condition”;

TYPES OF JOINS

EQUI JOIN : It returns all rows from tables where there is a match. Tables are joined on columns that have the same datatype & size in table. It is also known as equality join or simple join or inner join.

SYNTAX:

SELECTfield1,field2 FROM table1,table2 WHERE table1.field=table2.field;

EXAMPLE

SQL>SELECT ename, dname FROM emp, dept WHERE emp.deptno=dept.deptno;

CARTESION JOIN : When the join condition is omitted the result is Cartesian join of two or more tables in which all the combinations of rows will be displayed. All the rows are joined to all rows of the second table.

SYNTAX

SQL>SELECT field1, field2 FROM table1, table2;

EXAMPLE

SQL>SELECT ename, dname FROM emp, dept;

OUTER JOIN : While using equi join we see that if there exists certain rows in one table which don’t have corresponding values in the second table thn those rows will not be selected. We can forcefully select those rows by outer join. The rows for those columns will have NULL

values.

SYNTAX

SELECT table1.col, table2.col FROM table1, table2 WHERE table1.col (+) = table2.col;

EXAMPLE

SQL>SELECT empno, ename, emp.deptno, dname FROM emp, dept WHERE emp.deptno (+) = dept.deptno;

SELF JOIN : The self join can be seen as join of two copies of the same table. The table is not actually copied but sql performs the command as though it were.

EXAMPLE

SQL>SELECT e.ename, m.ename FROM emp e, emp m WHERE e.mgr=e.empno;

EXPERIMENT NO: 8

AIM: TO UNDERSTAND USE AND WORKING OF SUB - QUERIES

THEORY: SUBQUERIES

A sub query is a form of an SQL statement that appears inside another SQL statement. It is also termed as nested query. The statement containing a sub query is called a parent statement. The parent statement uses the rows returned by the sub query. It can be used by the following commands:

To insert records in a target table. To create tables and insert records in the table created. To update records in a target table. To create views. To provide values for conditions in WHERE, HAVING, IN etc. used with SELECT,

UPDATE, and DELETE statements.

TYPES OF SUB QUERIES

SINGLE ROW

It returns one row from inner nested query.

EXAMPLE IS:

SQL>SELECT deptno FROM emp WHERE ename =’MILLER’;

MULTIPLE ROW

Subqueries that return more than one row called multiple row queries. Operators like IN,ALL,ANY are used.

EXAMPLE

SQL>SELECT ename,sal,deptno FROM emp WHERE sal IN (SELECT min(sal) FROM emp GROUP BY deptno);

EXPERIMENT NO: 9

AIM: TO MAKE USE OF TRANSACTION CONTROL STATEMENTS VIZ ROLLBACK, COMMIT AND SAVEPOINT

THEORY:

SQL-Transaction Statements control transactions in database access. This subset of SQL is also called the Data Control Language for SQL (SQL DCL).

A transaction is a sequence of one or more SQL statements that together form a logical

unit of work. The SQL statements that form the transaction are typically closely related

and perform interdependent actions. Each statement in the transaction performs some

part of a task, but all of them are required to complete the task. Grouping the statements

as a single transaction tells the DBMS that the entire statement sequence should be executed atomically—all of the statements must be completed for the database to be in a

consistent state. A transaction mechanism, that ideally would guarantee the ACID properties, in order to ensure data integrity, despite concurrent user accesses (concurrency control), and faults (fault tolerance).

Transaction control statements are used to either save the modified data or to undo the changes if they were made in error. Until the data has been permanently saved to the table, no other users will be able to view any of the changes you have made. A transaction is a term used to describe a group of DML statements representing data actions that logically should be performed together.

COMMIT and ROLLBACK

SQL supports database transactions through two SQL transaction processing

Statements

COMMIT and ROLLBACK statement syntax diagrams

The COMMIT statement signals the successful end of a transaction. It tells the DBMS

that the transaction is now complete; all of the statements that comprise the

transaction have been executed, and the database is self-consistent.

The ROLLBACK statement signals the unsuccessful end of a transaction. It tells the

DBMS that the user does not want to complete the transaction; instead, the DBMS

should back out any changes made to the database during the transaction. In effect,

the DBMS restores the database to its state before the transaction began.

The COMMIT and ROLLBACK statements are executable SQL statements, just like

SELECT, INSERT, and UPDATE.

A COMMIT statement ends the transaction successfully, making its database changes

permanent. A new transaction begins immediately after the COMMIT statement.

A ROLLBACK statement aborts the transaction, backing out its database changes. A

new transaction begins immediately after the ROLLBACK statement.

About SAVEPOINT

A SAVEPOINT is a marker within a transaction that allows for a partial rollback. As changes are made in a transaction, we can create SAVEPOINTs to mark different points within the transaction. If we encounter an error, we can rollback to a SAVEPOINT or all the way back to the beginning of the transaction.

SQL> INSERT INTO AUTHOR 2 VALUES ('A11l', 'john', 3 'garmany', '123-345-4567', 4 '1234 here st', 'denver', 5 'CO','90204', '9999');

1 row created.

SQL> savepoint in_author;

Savepoint created.

SQL> INSERT INTO BOOK_AUTHOR VALUES ('A111', 'B130', .20); 1 row created.

SQL> savepoint in_book_author;

Savepoint created.

SQL> INSERT INTO BOOK 2 VALUES ('B130', 'P002', 'easy oracle sql', 3 'miscellaneous', 9.95, 1000, 15, 0, '', 4 to_date ('02-20-2005','MM-DD-YYYY')); 1 row created.

SQL> rollback to in_author;

Rollback complete.

In the example above, I inserted a row into the AUTHOR table and created a SAVEPOINT called in_author. Next, I inserted a row into the book_author table and created another SAVEPOINT called in_book_author. Finally, I inserted a row in the BOOK table. I then issued a ROLLBACK to in_author.

EXPERIMENT NO: 10

AIM: TO MAKE VIEWS OF A TABLE

THEORY:

VIEWS :

A view is very commonly used database object that is derived at runtime.

A view contains data of its own. Its contents are derived from another table. The command for creating view is CREATE VIEW command. Editing in the tables are automatically reflected in the views. It is virtual table & does not have any data of its own.

SYNTAX TO CREATE A VIEW IS:

SQL>CREATE [OR REPLACE] VIEW view name AS sub query

[WITH CHECK OPTION] [WITH READ ONLY];

EXAMPLE IS:

SQL>CREATE VIEW monika AS SELECT empno, ename, sal, comm FROM emp;

TYPES OF VIEWS

JOIN VIEW

It is defined as view that has more than one table specified in from clause and does not contain following clauses i.e. distinct, aggregation, group by. This type of view allows update, insert and delete command to change data in table.

SYNTAX

SQL>CREATE OR REPLACE VIEW monika AS SELECT ename, empno, sal FROM emp, dept WHERE emp.deptno = dept.deptno;

The views to be updateable must not include the following are

o Set operators , aggregate functionso Distinct operator , rownum pseudo columnso Group by clause , having clause

INLINE VIEW

Oracle also offers an inline view that is very handy and inline view is part of SQL statements. It allows you in body of SQL statement to define SQL for view that SQL statement will use to resolve its query.

MATERIALIZED VIEW

Snapshot also called materialized view. It is defined as copy of part of table or entire table. It reflects the current status of table that is being copied. The original status table is also called master table. Two types are Read only and update. Read-only does not allow changes to be made in view. It simply publishes and subscribes the replications. It allows changes in local copy which periodically updates master table.