Sql server introduction to sql server

Introduction
• MS SQL Server is a database server
• Product of Microsoft
• Enables user to write queries and other SQL statements and execute them
• Consists of several features. A few are:
– Query Analyzer
– Profiler
– Service Manager
– Bulk Copy Program (BCP)

Profiler
• Monitoring tool
• Used for performance tuning
• Uses traces – an event monitoring protocol
• Event may be a query or a transaction like logins etc

Service Manager
• Helps us to manage services
• More than one instance of SQL server can be installed in a machine
• First Instance is called as default instance
• Rest of the instances (16 max) are called as named instances
• Service manager helps in starting or stopping the instances individually

Instances
• Each instance is hidden from another instance
• Enhances security
• Every instance has its own set of Users, Admins, Databases, Collations
• Advantage of having multiple instance is
– Multi company support (Each company can have its own instance and
create databases on the same server, independent on each other)
– Server consolidation (Can host up to 10 server applications on a single
machine)

BCP
• Bulk Copy Program
• A powerful command line utility that enables us to transfer large number
of records from a file to database
• Time taken for copying to and from database is very less
• Helps in back up and restoration

Query Analyzer
• Allows us to write queries and SQL statements
• Checks syntax of the SQL statement written
• Executes the statements
• Store and reload statements
• Save the results in file
• View reports (either as grid or as a text)

SQL Database Objects
• A SQL Server database has lot of objects like
– Tables
– Views
– Stored Procedures
– Functions
– Rules
– Defaults
– Cursors
– Triggers

System Databases
• By default SQL server has 4 databases
– Master : System defined stored procedures, login details,
configuration settings etc
– Model : Template for creating a database
– Tempdb : Stores temporary tables. This db is created when the server
starts and dropped when the server shuts down
– Msdb : Has tables that have details with respect to alerts, jobs. Deals
with SQL Server Agent Service

Creating a database
• We need to use Master database for creating a database
• By default the size of a database is 1 MB
• A database consists of
– Master Data File (.mdf)
– Primary Log File (.ldf)

Database operations
• Changing a database
Use <dbname>
• Creating a database
Create database <dbname>
• Dropping a database
Drop database <dbname>

SQL Server Data types
• Integer : Stores whole number
• Float : Stores real numbers
• Text : Stores characters
• Decimal: Stores real numbers
• Money : Stores monetary data. Supports 4 places after decimal
• Date : Stores date and time
• Binary : Stores images and other large objects
• Miscellaneous : Different types special to SQL Server.
(Refer to notes for more info)

Operators
• Arithmetic
• Assignment
• Comparison
• Logical
• String
• Unary
• Bitwise

Select Statements
• To execute a statement in MS SQL, Select the statement and Click on the Execute
button in the query analyser or press F5
• This is used to retrive records from a table
• Eg. Select * from table1;
– This will fetch all rows and all columns from table1
• Eg. Select col1,col2 from table1
– This will fetch col1 and col2 from table1 for all rows
• Eg. Select * from table1 where <<condn>>
– This will fetch all rows from table1 that satisfies a condition
• Eg. Select col1,col2 from table1 where <<condn>>
– This will fetch col1 and col2 of rows from table1 that satisfies a condition

Select Options
• Aggregate functions
– Sum(col1): sum of data in the column col1
– Max(col1): data with maximum value in col1
– Min(col1): data with minimum value in col1
– Avg(col1): Average of data in col1
– Count(col1): Number of not null records in table
• Grouping – Group by col1 : Groups data by col1
• Ordering – Order by col1 : Orders the result in ascending order (default
order) of col1
• Filtering – Where <<condn>> and Having <<condn>>

Table management
Create table tablename
(
col1 data type,
col2 data type
);
- Creates a table with two columns
Drop table tablename;
- Drops the table structure

Insert statements
• Inserting data to all columns
– Insert into tablename(col1,col2) values(v1,v2)
– Insert into tablename values(v1,v2)
• Inserting data to selected columns
– Insert into tablename(col1) values (v1)
– Insert into tablename(col2) values (v2)

Update statement
Update table tablename
Set colname=value
- This updates all rows with colname set to value
Update table tablename
Set colname=value
Where <<condition>>
- This updates selected rows with colname as value only if the row
satisfies the condition

Delete statements
Delete from table1;
Deletes all rows in table1
Delete from table1 where <<condition>>
Deletes few rows from table1 if they satisfy the condition

Truncate statement
• Truncate table tablename
• Removes all rows in a table
• Resets the table.
• Truncate does the following, where as delete statement does not
– Releases the memory used
– Resets the identity value
– Does not invoke delete trigger

Alter statements
• Used to modify table structure
– Add new column
– Change data type of existing column
– Delete a column
– Add or remove constraints like foreign key, primary key

More table commands
• Viewing tables in a data base:
– Exec sp_tables “a%”
– This gives all tables in the current database that starts with “a”
• Viewing table strucure:
– Exec sp_columns <<tablename>>
– Exec sp_columns student;

Joins
• Cross Join
– Cartesian product. Simply merges two tables.
• Inner Join
– Cross join with a condition. Used to find matching records in the two
tables
• Outer Join
– Used to find un matched rows in the two tables
• Self Join
– Joining a table with itself

Cross Join
There are two tables A and B
A has a column Id and data (1,2,3)
B has a column Id and data (A,B)
If I put
Select A.Id, B.Id from A,B
This generates output as
A 1
B 1
C 1
A 2
B 2
C 2

Self Join
There is a table called Emp with the following structure:
empid ename mgrid
1 A null
2 B 1
3 C 1
4 D 2
If I want to print all managers using self join, I should write quey as:
select e1.ename from
emp e1,emp e2
where e1.mgrid = e2.empid

Inner Join
I have 2 tables Student(sid,Name) and Marks(Sid,Subject,Score)
If I want to print the marks of all students in the following format,
Name Subject Score
Select Name,Subject,Score from
Student s join Marks m
On s.sid = m.sid

Outer Join
• Right outer Join
– Print all the records in the second table with null values for missing
records in the first table
• Left outer Join
– Print all the records in the first table with null values for missing
records in the second table
• Full outer Join
– Prints all records in both the table with null values for missing records
in both the table

Left Outer Join
I have a table Employee (Eid, Ename, Mid) and
a table Machine (Mid,ManufacturerName)
Employee
Eid EName Mid
1 ABC 1
2 DEF 3
Machine
Mid ManufacturerName
1 Zenith
2 HP

Left Outer Join
I want to print the employee name and machine name.
If I write a query using inner join, then the second employee will
not be displayed as the mid in his record is not avilable with the second
table.
So I go for left outer join. The query is as shown below:
Select Ename, ManufacturerName from Employee e left outer join
Machine m on e.Mid = m.Mid

Right outer Join
Assume data in the tables like this:
Employee
Eid EName Mid
1 ABC 1
2 DEF
Machine
1 Zenith
2 HP

Right Outer Join
If I want to find which machine is unallocated, I can use right outer join.
The query is as follows:
Select Ename, ManufacturerName from Employee e right outer join
This yields a result
ABC Zenith
HP

Full Outer Join
Assume data in the tables like this:
Employee
Eid EName Mid
1 ABC 1
2 DEF
3 GHI 2
Machine
1 Zenith
2 HP
3 Compaq

Full Outer Join
If I want to find people who have been un allocated with a system and
machines that are been un allocated, I can go for full outer join.
Query is like this:
Select Ename, ManufacturerName from Employee e full outer join
This yields a result
ABC Zenith
DEF
GHI HP
Compaq

Views
• Views are logical tables
• They are pre compiled objects
• We can select few columns or rows from a table and put the data set in a
view and can use view in the same way as we use tables

Views
• Create views:
Create view viewname as select stmt
Create view view_emp as select empid,
empname from employee;
• Select from views:
Select * from viewname
Select empid,empname view_emp;
• Drop views:
Drop view viewname
Drop view view_emp;

String Functions
• Substring(string,start,length) – Will fetch characters starting at a specific
index extending to length specified.
• Left(string,length) – Fetches number of characters specified by length
from left of the string
• Right(string,length) – Fetches number of characters specified by length
from right of the string
• Len(string) – Returns the length of a string

String Functions
• Ltrim(string) – Removes leading spaces in a string
• Rtrim(string) – Removes trailing spaces in a string
• Lower(string) – Converts the characters in a string to lower case
• Upper(string) – Converts the characters in a string to upper case

Numeric Functions
• ABS(Number) – Fetches the modulo value (Positive value) of a number
• CEILING(Number) – Fetches the closest integer greater than the number
• FLOOR(Number) – Fetches the closest integer smaller than the number
• EXP(Number) – Fetches the exponent of a number

Numeric Functions
• POWER(x,y) – Fetches x raised to the power of y
• LOG(Number) – Fetches the natural logarithmic value of the number
• LOG10(Number) – Fetches log to the base 10 of a number
• SQRT(Number) – Fetches the square root of a number

Indexes
• Indexes make search and retrieve fast in a database
• This is for optimizing the select statement
• Types of index
– Unique
– Non unique
– Clustered
– Non clustered

Index
Create index indexname on
tablename(columnname)
This creates a non clustered index on a table
Create unique clustered index index_name on
Student(sname);
This creates a unique and clustered index on the
Column Sname.

Sequences
• This creates an auto increment for a column
• If a table has a column with sequence or auto increment, the user need
not insert data explicitly for the column
• Sequence is implemented using the concept of Identity

Identity
• Identity has
– A seed
– An increment
• Seed is the initial value
• Increment is the value by which we need to skip to fetch the nextvalue
• Identity(1,2) will generate sequence numbers 1,3,5,7…

Sample
Create table table1
(
Id integer identity(1,1),
Name varchar(10)
)
It is enough if we insert like this:
Insert into table1(name) values(‘Ram’);
Ram will automatically assigned value 1 for id

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Sql server introduction to sql server

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