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ASP.NET Programming
with C# and SQL Server
First Edition
Chapter 7
Working with Databases and
SQL Server Express
Objectives
In this chapter, you will:
• Study the basics of databases and SQL Server
• Work with SQL Server databases
• Define database tables
• Work with database records
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Introduction to Databases
• Database: an ordered collection of information
from which a computer program can quickly access
information
• Information in computer databases is stored in
tables similar to spreadsheets
• Record: a single complete set of related
information
• Field: an individual category of information stored
in a record
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Introduction to Databases (cont’d.)
Figure 7-1 Employee directory database
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Introduction to Databases (cont’d.)
• Flat-file database: stores information in a single
table
– Useful for simple collections of information
• Relational database: stores information across
multiple related tables
– Better for large and complex databases
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Understanding Relational Databases
• Relational databases consist of one or more
related tables
• Primary table: the main table in a relationship that
is referenced by another table
• Related (or child) table: references a primary table
in a relational database
• Tables in a relationship are connected using
primary and foreign keys
– Primary and foreign keys link records across multiple
tables
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Understanding Relational Databases
(cont’d.)
• Primary key: a field that uniquely identifies a
record in a table
• Foreign key: a field in a related table that refers to
the primary key in a primary table
• Index: a field that identifies records in a database
to make retrievals and sorting faster
– Primary key is a type of index
– Index may consist of one field or a combination of
multiple fields
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Understanding Relational Databases
(cont’d.)
• Three basic types of relationships in a relational
database:
– One-to-one
– One-to-many
– Many-to-many
• One-to-one relationship: there is exactly one
record in a related table for each record in the
primary table
– Used to break information into multiple, logical sets
– Information in a one-to-one relationship could be
placed within a single table
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Understanding Relational Databases
(cont’d.)
Figure 7-2 One-to-one relationship
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Understanding Relational Databases
(cont’d.)
• One-to-many relationship: one record in a
primary table has many related records in a related
table
– Used to eliminate redundant information
– Only the primary and foreign keys are duplicated
• Normalization: the process of breaking tables into
multiple related tables to reduce redundant and
duplicate information
– Reduces the overall size of the database
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Understanding Relational Databases
(cont’d.)
Figure 7-3 Table with redundant information
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Figure 7-4 One-to-many relationship
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Understanding Relational Databases
(cont’d.)
• Many-to-many relationship: many records in one
table are related to many records in another table
• Junction table: creates a one-to-many relationship
for each of the two tables in a many-to-many
relationship
– Contains foreign keys from the two tables in the
many-to-many relationship
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Figure 7-5 Many-to-many relationship
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Working with Database Management
Systems
• Database management system (or DBMS): an
application or collection of applications used to
access and manage a database
• Schema: the structure of a database
– Includes its tables, fields, and relationships
• Flat-file database management system: stores
data in a flat-file format
• Relational database management system (or
RDBMS): stores data in a relational format
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Working with Database Management
Systems (cont’d.)
• Popular commercial relational database
managements systems include:
–
–
–
–
–
Microsoft SQL Server
Oracle
Sybase
Informix
Microsoft Access
• Popular open source relational database
management systems include:
– MySQL
– PostgresSQL
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Working with Database Management
Systems (cont’d.)
• Functions of a DBMS:
–
–
–
–
–
–
Creating new database files
Allowing users to enter and manipulate data
Structuring and preservation of the database file(s)
Ensuring that data is stored correctly in tables
Ensuring that relationships are enforced
Providing authentication and authorization features
• Query: a structured set of instructions and criteria
for retrieving, adding, modifying, and deleting
database information
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Working with Database Management
Systems (cont’d.)
• Data manipulation language (or DML): a
language for creating queries
• Structured Query Language (or SQL): supported
by most DBMSs for creating queries
• Most DBMSs provide an interface to design queries
– Must still learn SQL for programmatically accessing
a database
• Each DBMS creates its own proprietary file types
– Most have the ability to import data from other file
formats but cannot directly read each other’s files
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Querying Databases with Structured
Query Language
• SQL has become an official standard for querying
databases
• SQL statements are composed of keywords that
perform actions on a database
• SELECT statement returns data from the database
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Querying Databases with Structured
Query Language (cont’d.)
Table 7-1 Common SQL keywords
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Getting Started with SQL Server
• Microsoft SQL Server Management Studio
Express: a graphic tool for manipulating SQL
Server databases
• New Query window: used to execute SQL
commands
• SQL Server Query Designer: a graphic tool for
creating queries in a graphical environment
– Can drag fields from table objects or can center SQL
commands directly
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Getting Started with SQL Server
(cont’d.)
Figure 7-6 Microsoft SQL Server Management Studio Express
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Getting Started with SQL Server
(cont’d.)
Figure 7-7 Query window in SQL Server Management Studio Express
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Getting Started with SQL Server
(cont’d.)
Figure 7-8 Query Designer in SQL Server Management Studio Express
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Installing SQL Server 2008
Management Studio Express
• To install SQL Server Management Studio Express:
– Download the installation package from Microsoft’s
Web site
– Start the installation package that you downloaded
– Select Installation link
– Select New SQL Server stand-alone installation or
add features to an existing installation link
– Follow the rest of the on-screen instructions to
complete the installation
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Working with the SQL Server
Management Studio Express
• Query window allows you to enter SQL commands
– Does not have a graphical interface
• SQL commands must be terminated with a
semicolon
– If no semicolon, the query window assumes you
want to enter more SQL statements
• From the Query menu, select Execute to execute
the SQL commands in the query window
• Results window displays the results of executing
the SQL commands
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Figure 7-9 Results window showing results of a SQL query
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Working with the SQL Server
Management Studio Express (cont’d.)
Figure 7-10 Output from a multiline SQL command
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Understanding SQL Server Identifiers
• You must define identifiers (names) for
databases, tables, fields, and indexes
• Two types of identifiers:
– Regular identifiers: must begin with a letter,
underscore (_), number sign (#) or at sign (@)
– Delimited identifiers: enclosed by double
quotations (“”) or brackets ([]), and may contain
spaces or other characters not allowed in regular
identifiers
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Understanding SQL Server Identifiers
(cont’d.)
• To use SQL Server Management Studio Express,
you must connect to a server
• Instance: refers to a single SQL Server database
– An installation of SQL Server can have many
instances
– Default instance is named SQLEXPRESS
• Authentication types:
– Windows Authentication
– SQL Server Authentication
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Understanding SQL Server Identifiers
(cont’d.)
Figure 7-11 Connect to Server dialog box
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Working with SQL Server Databases
• The basics of working with databases in SQL
Server include:
–
–
–
–
–
Creating databases
Deleting databases
Specifying field data types
Creating tables
Deleting tables
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Creating Databases
• Use the CREATE DATABASE statement to create a
new database
• Syntax:
CREATE DATABASE databaseName;
– databaseName must be unique
• New databases are created with a file extension of
.mds
• Can specify the location for the database using the
FILENAME keyword
• Must define tables and fields after creating the
database
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Deleting Databases
• Use the DROP DATABASE statement to delete a
database
– This removes all tables from the database and
deletes the database itself
• Syntax:
DROP DATABASE databaseName;
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Specifying Field Data Types
• Fields in a database store data according to type
– Data type determines the amount of memory and
storage space required for the field
• SQL Server includes numeric, string, monetary,
and date/time data types
• Choose the smallest data type possible for each
field
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Table 7-2 Common SQL Server data types
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Creating Tables
• Use the CREATE TABLE statement to specify the
table, the column names, and the data type for
each column
• Syntax:
CREATE TABLE tableName (columnName Type, …);
• Column names must be unique within a table
• Table names must be unique with the database
• Must select the database with the USE database
statement first to use it in a query window
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Deleting Tables
• Use the DROP TABLE statement to remove all data
from a table and delete the table definition
• Syntax:
DROP TABLE tableName;
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Working with Records
• Working with records includes:
– Adding records to a table
– Modifying existing records in a table
– Deleting existing records in a table
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Adding Records
• Use the INSERT statement to add a single new
record to a table
• Syntax:
INSERT INTO tableName VALUES (value1,value2,…);
• Text values are enclosed within single quotations
• Values in the VALUES list must be in the same order
in which the fields are defined in the table
– Specify NULL in any fields for which you do not have a
value
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Adding Records (cont’d.)
• Use the BULK INSERT statement with a local text
file to add multiple records to an existing database
• Syntax:
BULK INSERT tableName FROM ‘filePath’;
• Each record in the text file should be on a separate
line with tabs between each field
– Leave empty fields blank
• Values on each line must be in the same order as
the fields are defined in the table
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Adding Records (cont’d.)
Figure 7-12 Results window after adding records to the outlook
table in the forecast database
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Retrieving Records
• Use a SELECT statement to retrieve records
from a table
• Syntax:
SELECT criteria FROM tableName;
• Use * to select all fields, or list individual field
names separated by commas
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Retrieving Records (cont’d.)
Figure 7-13 Individual fields returned with a SELECT statement
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Sorting Query Results
• Use the ORDER BY keyword with the SELECT
statement to sort results alphanumerically
• Syntax:
SELECT criteria FROM tableName
ORDER BY fieldName;
• Add the DESC keyword to sort in reverse (in
descending order)
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Sorting Query Results (cont’d.)
Figure 7-14 Results returned from inventory table of the skateboards
database sorted by price
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Sorting Query Results (cont’d.)
Figure 7-15 Results returned from inventory table of the skateboards
database reverse sorted by price
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Filtering Query Results
• Use the criteria portion of the SELECT
statement to determine which fields to retrieve from
a table
• Use the WHERE keyword to specify which records to
return
• Syntax:
SELECT criteria FROM tableName
WHERE condition;
• Can use AND and OR keywords to specify more
detailed conditions in the WHERE clause
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Filtering Query Results (cont’d.)
Figure 7-16 Results returned from the inventory table of the skateboards
database where price is less than 100
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Filtering Query Results (cont’d.)
Figure 7-17 Results returned from the inventory table of the skateboards
database where price is greater than 100 and length is less than 30
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Filtering Query Results (cont’d.)
Figure 7-18 Results returned from the inventory table of the skateboards
database where price is greater than 100 or length is less than 30
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Updating Records
• Use the UPDATE statement to update existing
records in a table
• Syntax:
UPDATE tableName
SET columnName=value
WHERE condition;
• Must use a WHERE condition to specify which
record to update
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Deleting Records
• Use the DELETE statement to delete existing
records in a table
• Syntax:
DELETE FROM tableName
WHERE condition;
• Must use the WHERE clause to specify which
record(s) to delete
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Summary
• A database is an ordered collection of information
from which a computer program can quickly access
information
• A record is a single complete set of related
information
• Fields are individual categories of information
stored in a record
• Flat-file database stores information in a single
table
• Relational database stores information across
multiple tables
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Summary (cont’d.)
• A query is a structured set of instructions and
criteria for retrieving, adding, modifying, and
deleting database information
• Structured Query Language (SQL) has become a
standard data manipulation language for many
database management systems
• Microsoft SQL Server Management Studio Express
is a graphic tool for manipulating a SQL Server
database
• Regular identifiers begin with a letter, underscore,
number sign, or at sign
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Summary (cont’d.)
• Delimited identifiers allow spaces and other
characters, enclosed within double quotations or
brackets
• Use the USE statement to select a database to
work with
• Use the CREATE DATABASE statement to create a
new database
• Use the DROP DATABASE statement to delete a
database
• Choose the smallest data type possible for each
field in a table
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Summary (cont’d.)
• Use the CREATE TABLE statement to create a
new table and specify the column names and data
types
• Use the DROP TABLE statement to delete a table
• Use the INSERT statement to add a single record
to a table
• Use the BULK INSERT statement to add multiple
records to a table from a local text file
• Use the SELECT statement to retrieve records from
a table
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Summary (cont’d.)
• Use the ORDER BY keyword in a SELECT
statement to sort the results returned by a query
• Use the WHERE keyword to specify which records to
return from a database
• Use the UPDATE statement to update records in a
table
• Use the DELETE statement to delete records in a
table
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