SQLIntroduction

8/7/2019 SQLIntroduction

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SQL

SQL Server : Overview

SQL : Overview Types of SQL

Database : Creation

Tables : Creation & Manipulation Data : Creation & Manipulation

Data : Retrieving using SQL


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SQL : Overview

Is the standard command set used to

communicate with the relational databasemanagement systems

Can do Creating databases, Creating tables,

Querying and Manipulating data and

granting access to the users

English like structure

is by nature flexible


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Types of SQL Commands

SQL statements are divided into the

following categories Data Definition Language (DDL)

Data Manipulation Language (DML)

Data Query Language (DQL) Data Control Language (DCL)

Data Administration Statements (DAS)

Transaction Control Statements (TCS)


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Data Definition Language

Is used to create, alter and delete database

objects The commands used are

CREATE

ALTER

DROP


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Data Manipulation Language

Used to insert data into the database,

modify and delete the data in the database Three DML statements

INSERT

UPDATE

DELETE


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Data Query Language

This statement enables you to query one or

more tables to get the information commonly used SQL statements

SQL has only one data query statement

SELECT


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Data Control Language

The DCL consists of commands that

control the users access to the databaseobjects

The DCL is mainly related to the security

issues

The DCL commands are

GRANT - Giving access to the data

REVOKE - Denying access to the data


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Data Administration Statements

DASs allow the user to perform audits and

analysis on operations within the database. Used to analyze the performance of the

system

Data Administration commands are

START AUDIT

STOP AUDIT


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Transaction Control Statements

TCSs are statements, which manage all the

changes made by the DML statements Some of the TCSs are

COMMIT

ROLLBACK

SAVEPOINT

SET TRANSACTION


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Databases

Collection of related data and manipulation

of that data Can create database using SQL command

CREATE DATABASE databasename


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Tables

Are the basic building blocks in any

RDBMS contains rows and columns of data

using DDL commands, we can create , alter

and delete tables

Creation of table includes the properties of

the columns


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Create statement

CREATE TABLE table-name

(column-1-definition[,column-2-definition] ..

[,column-n-definition]

[,primary key (column name)][.alternate key (column name)]

[,Foreign key (column name) ]);


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Column definition columnName data-type [NULL | NOT NULL

[WITH DEFAULT | UNIQUE]]

NULL - RDBMS insert a null in that column if

the user does not specify a value

NOT NULL - column should have a value

WITH DEFAULT - the RDBMS will substitute

the default values

UNIQUE - no duplicate values will be allowed


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Data types char(n) - represents a fixed length of string of n

characters where n>0 and is an integer

varchar(n) - varying length string whose maxlength is n

bit(n) - represents a fixed length string of exactly

n bits decimal(p, q) - represents a decimal number, p

digits and with decimal point q digits from

right


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Data Types

float(n) - represents the floating point

number

int - represents a signed integer

datetime - represents the date/time

money - represents the currency


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2nd form of CREATE

CREATE TABLE new-table-name LIKE

table-name

when a table is created from an existing

table only the structure is copied; the

primary, alternate and foreign key

definitions is not inherited


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Modifying a Table

An existing table can be modified by using

the ALTER TABLE statement

ALTER TABLE table-name

ADD column definition

ALTER TABLE table-nameAdd CONSTRAINT constraint name

Primary key (column name)


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Deleting a table

An existing table can be deleted at any time

by using the DROP TABLE statement

DROP TABLE table-name

specified table is deleted from the system

all the data for that table also will bedeleted


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Inserting rows into a table INSERT INTO table-name

[[column [,column].]]

values [literal[,literal]]]; a single row is inserted into the table, having

specified columns

INSERT INTO table-name

[[column [,column].]]

subquery;

the subquery is evaluated first and a copy of the

result(usually multiple rows) is inserted into the table


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Updating fields in a row

UPDATE table-name

SET column-name = expr[WHERE condition]

table-name : table for the data to be updated

SET clause : the set of new values to be set WHERE clause : condition will be checked

and particular record gets updated


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Deleting of data from the table

DELETE FROM table-name

WHERE condition Depending on the condition the record will

be deleted from the table


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SELECT statements

SELECT - A keyword that tells the

database this command is a query. All

queries begin with this word followed by a

space

the select command simply instructs the

database to retrieve information from a

table


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Different features applied to a simple

statement

All columns

Qualified Retrieval Eliminating Duplicates

Using Boolean(IN, BETWEEN, LIKE)

Using Escape clause Computed values

Involving nulls


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All Columns

SELECT * FROM Table-name

Qualified Retrieval

SELECT * FROM table-name

WHERE condition

can use all comparision operators (=, , , =) in the WHERE clause

can contain multiple comparison with AND, OR,NOT

Eliminating Duplicates

SELECT DISTINCT column-name FROM table-

name


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Using Boolean Operators

IN


WHERE column-name IN (val1, val2, val3);

BETWEEN SELECT * FROM table-name

WHERE column-name BETWEEN val1 and val2

between is an inclusive operator values matching either of the boundary values

cause the predicate to be true


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NOT BETWEEN


WHERE column-name NOT BETWEEN val1 and

val2

LIKE SELECT * FROM table-name

WHERE column-name LIKE string%

LIKE _% Escape Sequence


WHERE column-name LIKE %\_%


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Computed Values SELECT column1, column2Expression

FROM table-name

WHERE condition

NULLS


WHERE column-name IS NULL

ORDER BY


ORDER BY column-name DESC

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