What is Business Requirement Document ?

Filtering and Sorting data using SQL statements

 Filtering & Sorting Data using SQL 

 

Once you know the basics (SELECT, FROM, WHERE), filtering and sorting helps you get the exact rows from tables .

 1. Filtering with Conditions (AND, OR, NOT) 

- Use WHERE to filter rows.

- Combine with logical operators: 

  • AND: all conditions true 

  • OR: any condition true 

  • NOT: negate condition 

-- All conditions true (AND)

SELECT * FROM employees

WHERE department = 'Sales'   AND salary > 50000;

-- Any condition true (OR)

SELECT * FROM employees

WHERE department = 'Sales'    OR department = 'Marketing';

-- Negate condition (NOT)

SELECT * FROM employees

WHERE NOT department = 'HR';

 

2.Pattern Matching with LIKE 

- % = any sequence, _ = single char 

  • Names starting with 'J' 

  • Names with 4 letters starting with 'J' 

-- Names starting with 'J'

SELECT * FROM customers

WHERE name LIKE 'J%';

-- Names with four letters starting with 'J'

SELECT * FROM customers

WHERE name LIKE 'J___';

 

3. Filtering with IN 

- Check if value matches any in list 

  SELECT * FROM products WHERE category IN ('Electronics', 'Furniture'); 

 

4. Range Checking with BETWEEN 

- Filter values in a range (inclusive) 

  SELECT * FROM orders WHERE order_date BETWEEN '2023-01-01' AND '2023-12-31'; 

 

5. Checking for NULL Values 

- Find NULL: 

  SELECT * FROM employees WHERE manager_id IS NULL;

- Find NOT NULL: 

  SELECT * FROM employees WHERE manager_id IS NOT NULL; 

 

6. Sorting with ORDER BY 

- Ascending (default): 

  SELECT * FROM employees ORDER BY salary; 

- Descending: 

  SELECT * FROM employees ORDER BY salary DESC; 

- Multiple columns: 

  SELECT * FROM employees ORDER BY department, salary DESC;

List Of Table Operations in SQL

 

List of Table Operations in SQL [1. CREATE, 2. INSERT, 3.UPDATE, 4. ALTER, 5. DELETE, 6. DROP, 7. TRUNCATE ]

1.     CREATE : To define a new Table.

2.    INSERT : Add rows to the table.

3.    UPDATE : Modify existing rows in the table.

4.    ALTER : Modify the structure of the table.

5.    DELETE : Remove Rows from the table.

6.    DROP : Removes the entire table.

7.    TRUNCATE : Removes the all rows of the table but it keeps the table structure.

1>     CREATE : To define a new Table.

 

CREATE TABLE jobs (

job_id INT PRIMARY KEY,

job_title VARCHAR(100),

job_description TEXT,

min_salary DECIMAL(10, 2),

max_salary DECIMAL(10, 2)

);

 

2 INSERT : Add rows to the table

 INSERT INTO jobs (job_id, job_title, job_description, min_salary, max_salary)

VALUES

(100, ‘Manager’, ‘Manage the Team', 800000, 1500000);

 

3>  UPDATE : Modify existing rows in the table.

UPDATE jobs SET min_salary = 100000

WHERE job_id = 100;

Note : It will change the min salary to 100000 from 800000 for the job_id 100.

4>  ALTER : Modify the structure of the table.

ALTER TABLE jobs ADD COLUMN dept_id INT;

 

5> DELETE : Remove Rows from the table

DELETE FROM jobs WHERE job_id = 100;

6> DROP : Removes the entire table.

DROP TABLE jobs;

7> TRUNCATE : Removes the all rows of the table but it keeps the table structure

TRUNCATE TABLE jobs;

Note : >  It removes all rows from the table.

Ø  It retains the Table Structure

Ø  It is faster then DELETE statement

 

 #sql #create #drop #delete #truncate #alter #update #sql_statement

 

Oracle Interview Questions and Answers

 Coming Soon. 

The "Dual Table" in Oracle

> The "DUAL" table is a one row and one column table. The owner of this table is "SYS" but it's accessible to all the db users. 

> It is having single column called as "DUMMY"

> It is used to test SQL expression with out querying to the main/real tables. 

Eg : 1> SELECT SYSDATE FROM DUAL;

O.P : It will print current date and time. 

    

2> SELECT 'Hello, Welcome to SQL' from DUAL;

O.P : 

3> SELECT 5*9 AS RESULT FROM DUAL;

O.P: 

#SQL #LEARNSQL #DUALTABLE

About Oracle Buffer

About Oracle Buffer :-

• All Commands of SQL are typed at the SQL prompt.
• Only one SQL statement is managed in the SQL buffer.
• The current SQL statement replaces the previous SQL statement in the buffer.
• The SQL statements can be divided into different lines within the SQL buffer.
• Only one line i.e, the current line can be active at a time in the SQL buffer.
• At SQL prompt, editing is possible only in the current SQL buffer line.
• Every statement of SQL should be terminated using semi colon ";".
• One sql statement can contain only one semi colon.
• To run the previous or current SQL statement in the bufer type "/" at SQL prompt.
• To open the SQL editor type "ED" at SQL prompt.

Introduction to SQL

INTRODUCTION : -

• SQL usually pronounced as “Sequel” stands for Structured Query Language.
• SQL is the native language of the Oracle Server. It is the language used to communicate with the database. Again SQL consists of SQL statements and SQL*Plus commands. SQL statements are used to talk to the database. When you enter a SQL statement, it is stored in a part of the memory called the SQL Buffer and remains there until a new statement is entered. SQL*Plus is an Oracle tool that recognizes and submits 
• SQL statements to the Oracle server for execution and contains its own command language.

Features of SQL:-

• It is very easy to write, it can be used by all kinds of users with little or not programming experience.
• It is a non-procedural language.
• It reduces the amount of time required for creating and maintaining systems.
• It is based on American National Standards Iinstitute (ANSI) standard SQL.
• It manipulates data and tables definition in the database.
• It is entered into SQL buffer on one or more lines.
• It does not have a continuation character.
• It cannot be abbreviated.
• It uses a termination character to execute command immediately.
• Uses functions to perform some formatting.

Features of SQL*Plus :-

• Recognizes SQL statements and sends them to the server.
• It accepts SQL input from files.
• It provides a line editor for modifying SQL statements.
• It controls environmental settings.
• Accesses local and remote databases.
• It doesn’t allow manipulation of values in the database.
• It is entered one line at a time and is not stored in the SQL buffer.
• Has a dash(-) as a continuation character if command exceed one line.
• Doesn’t require any termination character, commands are executed immediately.
• It uses commands to format data.

Advantages of SQL :-

• SQL is a high level language that provides a greater degree of abstraction than procedural languages. It is designed so that the programmer can specify what data is needed but need not specify how to retrieves it.
• Applications written in SQL can be easily ported across systems.
• SQL as a language is independent of the way it is implemented internally.
• The language even being simple and easy to learn can handle complex situations.
• It is not just a query language, it can be used to define data structures, control access to the data and delete, insert, modify occurrences of the data.
• The results to be expected are well defined i.e, there is no ambiguity about the way a query will interpret the data and produce the result.

Types of SQL :-

SQL can be classified on the basis of its various functionality, listed below.

• Querying data.
• Updating, inserting and deleting database objects.
• Controlling access to the database.
• Providing data integrity and consistency.

SQL statements are divided into following types.

1.  Data Definition Language (DDL)
2.  Data Manipulation Language (DML)
3.  Transaction Control Lauguage (TCL)
4.  Data Control Language (DCL)

    1)   Data Definition Language DDL) :-

The DDL commands enables you to perform :--

• CREATE statement.
• ALTER statement.
• DROP statement.
• RENAME statement.
• TRUNCATE statement.

The objects that can be created, altered, dropped are :-

Cluster, Database, Database link, Function, Index, Package, Package body, Procedure, Rollback segment, Role, Sequence, Synonym, Table, User, View.

    2)  Data Manipulation Language (DML) :-

A DML command is used when we want to add, update or delete data in the database. A collection of DM statements that form a logical unit of work is called a transaction.

The DML commands are :-

• INSERT statement.
• UPDATE statement.
• DELETE statement.

   3)  Transaction  Control Language (TCL) :-

As we know transaction is nothing but a set of inserts, updated and deletes (performed on the database) that form a logical unit of work. TCL is used to control these transactions i.e , whether or not a transaction should take place is controlled by TCL.

The TCL commands are :-

• COMMIT statement.
• ROLLBACK statement.
• SAVEPOINT statement.

    4)  Data Control Language (DCL) :-

The DCL commands enable you to grant or revoke user privileges and roles.

The DCL commands are :-

• GRANT statement.
• REVOKE statement.

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Oracle Object Oriented Concepts

An Object is a reusable application component that developers need to be aware of, rather than how it works. Object are basic entities in a system. They could represent a person, place, bank account, or any item that is handled by program. Every object consists of an attribute and one or more methods. An attribute could be any property of the object.

Class:

          It is a collection of attributes and functions (method) to plan the object.

Object Table :

·   Object table are created by using the user defined data types.

·      In an object table each row or record is treated as an object.

·      Each row in an object table has an object Identified (OID), which is unique through out       the   database.

·     The rows or objects of an object table can be referenced by other objects with in the  database.

·     An object table is created using the CREATE TABLE command.

·     All object types are associated with default method applied upon the relational tables , i.e    INSERT, DELETE, UPDATE and SELECT.

·   The relational DML operation style is accepted only when the user defined data type is a  collection of Build-in data types, and the object table doesn't contain any REF Constraints.

Creating an user defined Object type :-

Syntax

SQL> CREATE OR REPLACE TYPE

         

          Object (Element1 (size),

           (Element2 (size),

           (ElementN (size) );

             

•      All user defined data types are schema objects of the database.
•            The user defined object data type can be used as Reference in other tables.
•            All user defined data types and object are stored permanently in the Data dictionaries.
•            USER_TYPES
•            USER_OBJECTS
•            We can query for the uesr defined data types and objects using the relational SELECT.

  SQL> Select Type_Name, TypeCode,

          Attributes,Methods

          FROM USER_TYPES;

  SQL> Select Object_Name,

          Object_Type

          FROM USER_OBJECTS;

  Creating User Defined Address Type :-

  

  SQL> Create or Replace TYPE Addr_type AS OBJECT ( Hno VARCHAR2 (10),

                              Street VARCHAR2 (20), City VARCHAR2 (20), Pin NUMBER(6));

  SQL> Create or Replace TYPE PF_TYPE AS OBJECT ( PFNO NUMBER(6), AMT      NUMBER(12,2));

• The above statement create the user defined object data type called as Addr_type and      PF_TYPE in the data dictionary called USER_TYPES.
•            This data type is also called as collection in oracle, and this collection is reusable where ever   the same data type collection is expected in project development.

 Creating Table with user Defined Data Type :-

 SQL> CREATE TABLE EMPLOYEE ( ECODE NUMBER(3), NAME VARCHAR2(20),  ADDRESS ADDR_TYPE, BASIC NUMBER(12,2), PF PF_TYPE);

• Once the user defined data types are created we can instantiate them in the normal  relational tables.
•  These instances look as normal attributes with in the table, but can be operated only with  CONSTRUCTOR METHOD or OBJECT VIEWS.
•  In any of the operation we have to provide reference to all attributes with in the instance,  but partial association is not accepted.

SQL> Create table Supp_Det ( Rol number(3), Name varchar2(20),

          Saddr addr_type, COurse varchar2(20));

Inserting the data into EMPLOYEE Table :-

SQL> INSERT INTO EMPLOYEE VALUES (100, 'Ram', ADDR_TYPE ('130 A', 'CROSS LANE', 'HYBD', 500016), 8000, PF_TYPE(1200,400));

Select Data From OBJECT table:-

SQL> SELECT * FROM EMPLOYEE;

SQL> SELECT ADDRESS FROM EMPLOYEE

SQL> SELECT NAME, E.ADDRESS.CITY FROM EMPLOYEE E;

Note :- Alias is must to retrieve/manipulate Object elements.

Update data from Object Table:-

SQL> UPDATE EMPLOYEE E SET BASIC =BASIC+100 WHERE E.ADDRESS.CITY=’HYD’;

Deleting data from Object Table:-

SQL> DELETE FROM EMPLOYEE;

SQL> DELETE FROM EMPLOYEE E WHERE E.PF.PFNO=1200;

Creating User Defined Emp Det Type:

SQL> Create type info As Object (code Number(4), Name Varchar2(20), Hno Varchar2(10), Street Varchar2(20), City Varchar2(20), Pin Number(6));

Creating an Object Table:-

• Is a table which is entirely build from the abstract type.

Syntax

       Create Table (Table_Name) of (Object Name);

Inserting Rows into Object Table:-

•           To insert a record into an Object Table we may use the CONSTRUCTOR METHOD of the actual data type or directly implement the RELATIONAL INSERT statement.
•          The Normal; INSERT or RELATION INSERT is possible only when the table does not contain any nested data types.

Relation Insert:-

SQL> Insert into Emp_info Values(1001, ‘ram’, ‘12-123’, ‘AMEERPET’,’MGS’,’BLORE’,516217);

Inserting Using Construct Method:-

SQL> Insert into Emp_info values(info(1002,’suman’,’12-124’,’vijiinag’,’blore’,516217);

SQL> Create table supp_info of Info;

Order By Clause

• This clause in a select statement arranges the data on a specified column in ascending or in descending order.
• This clause will work after the execution of select statement.
• By default it arranges the data in ascending order.
• In order to arrange the data in descending order , an option called DESC is used.
• Data is arranged in order over a required column for temporary.
• Order by clause can be specified with one or more columns.

      Examples :-

        Display empno, ename and salary of all the employees arranging salaries in ascending order.

        Ans : Select empno, ename, sal from emp order by sal;

        Display ename, job, salary, deptno, commission, and hiredate of all those employees who are working as CLERK, SALESMAN and they have been hired in the year 81 and they don’t earn any commission. Arrange the data in ascending order of salary.

        Ans : Select ename, job, sal, deptno , comm, hiredate from emp

          Where job IN(‘CLERK’ , ‘SALESMAN’) AND

          Hiredate LIKE ‘%81’ AND

          Comm IS NULL

          Order by sal;

        Display ename, job, sal of all the employees arranging job in ascending order and salary in descending order.

        Ans : Select ename, job, sal from emp

          Order by job, sal desc;

        Display ename, job, sal of all those employees arranging job and sal in ascending order.

        Ans : Select ename, job, sal from emp

          Order by job, sal;