SQL SQL Server : Overview SQL : Overview Types of SQL Database : Creation Tables : Creation & Manipulation Data : Creation & Manipulation Data : Retrieving using SQL

SQL : Overview Is the standard command set used to communicate with the relational database management systems Can do Creating databases, Creating tables, Querying and Manipulating data and granting access to the users English like structure is by nature flexible

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)

Data Definition Language Is used to create, alter and delete database objects The commands used are CREATE ALTER DROP

Data Manipulation Language Used to insert data into the database, modify and delete the data in the database Three DML statements INSERT UPDATE DELETE

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

Data Control Language The DCL consists of commands that control the user’s access to the database objects 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

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

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

Databases Collection of related data and manipulation of that data Can create database using SQL command CREATE DATABASE databasename

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

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) ]);

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

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 max length 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

Data Types float(n) - represents the floating point number int - represents a signed integer datetime - represents the date/time money - represents the currency

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

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-name Add CONSTRAINT constraint name Primary key (column name)

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 be deleted

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

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

Deleting of data from the table DELETE FROM table-name WHERE condition Depending on the condition the record will be deleted from the table

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

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

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

Using Boolean Operators IN SELECT * FROM table-name 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

NOT BETWEEN SELECT * FROM table-name WHERE column-name NOT BETWEEN val1 and val2 LIKE SELECT * FROM table-name WHERE column-name LIKE ‘string%’ LIKE ‘_%’ Escape Sequence SELECT * FROM table-name WHERE column-name LIKE ‘%\_%’

Computed Values SELECT column1, column2Expression FROM table-name WHERE condition NULLS SELECT * FROM table-name WHERE column-name IS NULL ORDER BY SELECT * FROM table-name ORDER BY column-name DESC