mssql

MS SQL Server

Name: Janas KhanPresentation:General Discussion With Friends

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 databaseCreate database <dbname>

• Dropping a databaseDrop 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

14

SQL statement processing order

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 managementCreate 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 JoinThere are two tables A and BA has a column Id and data (1,2,3)B has a column Id and data (A,B)

If I putSelect A.Id, B.Id from A,BThis generates output as A 1B 1C 1A 2B 2C 2

Self JoinThere 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 JoinI 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 JoinI 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 JoinI 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 JoinAssume data in the tables like this:

Employee

Eid EName Mid

1 ABC 1

2 DEF

Machine

Mid ManufacturerName

1 Zenith

2 HP

Right Outer JoinIf 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

Machine m on e.Mid = m.Mid

This yields a result

ABC Zenith

HP

Full Outer JoinAssume data in the tables like this:

Employee

Eid EName Mid

1 ABC 1

2 DEF

3 GHI 2

Machine

Mid ManufacturerName

1 Zenith

2 HP

3 Compaq

Full Outer JoinIf 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

Machine m on e.Mid = m.Mid

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 stmtCreate view view_emp as select empid,empname from employee;

• Select from views:Select * from viewnameSelect empid,empname view_emp;

• Drop views: Drop view viewnameDrop 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

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…