1. ASP.NET Programming with C# and SQL Server First Edition
Chapter 7
Working with Databases and SQL Server Express

2. 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
ASP.NET Programming with C# and SQL Server, First Edition

3. 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
ASP.NET Programming with C# and SQL Server, First Edition

4. Introduction to Databases (cont’d.)
Figure 7-1 Employee directory database
ASP.NET Programming with C# and SQL Server, First Edition

5. 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
ASP.NET Programming with C# and SQL Server, First Edition

6. 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
ASP.NET Programming with C# and SQL Server, First Edition

7. 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
ASP.NET Programming with C# and SQL Server, First Edition

8. 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
ASP.NET Programming with C# and SQL Server, First Edition

9. Understanding Relational Databases (cont’d.)
Figure 7-2 One-to-one relationship
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10. 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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11. Understanding Relational Databases (cont’d.)
Figure 7-3 Table with redundant information
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12. Figure 7-4 One-to-many relationship
ASP.NET Programming with C# and SQL Server, First Edition

13. 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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14. Figure 7-5 Many-to-many relationship
ASP.NET Programming with C# and SQL Server, First Edition

15. 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
ASP.NET Programming with C# and SQL Server, First Edition

16. 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
ASP.NET Programming with C# and SQL Server, First Edition

17. 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
ASP.NET Programming with C# and SQL Server, First Edition

18. 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
ASP.NET Programming with C# and SQL Server, First Edition

19. 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
ASP.NET Programming with C# and SQL Server, First Edition

20. Querying Databases with Structured Query Language (cont’d.)
Table 7-1 Common SQL keywords
ASP.NET Programming with C# and SQL Server, First Edition

21. 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
ASP.NET Programming with C# and SQL Server, First Edition

22. Getting Started with SQL Server (cont’d.)
Figure 7-6 Microsoft SQL Server Management Studio Express
ASP.NET Programming with C# and SQL Server, First Edition

23. Getting Started with SQL Server (cont’d.)
Figure 7-7 Query window in SQL Server Management Studio Express
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24. Getting Started with SQL Server (cont’d.)
Figure 7-8 Query Designer in SQL Server Management Studio Express
ASP.NET Programming with C# and SQL Server, First Edition

25. 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
ASP.NET Programming with C# and SQL Server, First Edition

26. 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
ASP.NET Programming with C# and SQL Server, First Edition

27. Figure 7-9 Results window showing results of a SQL query
ASP.NET Programming with C# and SQL Server, First Edition

28. Working with the SQL Server Management Studio Express (cont’d.)
Figure 7-10 Output from a multiline SQL command
ASP.NET Programming with C# and SQL Server, First Edition

29. 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
ASP.NET Programming with C# and SQL Server, First Edition

30. 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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31. Understanding SQL Server Identifiers (cont’d.)
Figure 7-11 Connect to Server dialog box
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32. 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
ASP.NET Programming with C# and SQL Server, First Edition

33. 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
ASP.NET Programming with C# and SQL Server, First Edition

34. 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;
ASP.NET Programming with C# and SQL Server, First Edition

35. 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
ASP.NET Programming with C# and SQL Server, First Edition

36. Table 7-2 Common SQL Server data types
ASP.NET Programming with C# and SQL Server, First Edition

37. 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
ASP.NET Programming with C# and SQL Server, First Edition

38. 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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39. 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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40. 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
ASP.NET Programming with C# and SQL Server, First Edition

41. 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
ASP.NET Programming with C# and SQL Server, First Edition

42. Adding Records (cont’d.)
Figure Results window after adding records to the outlook table in the forecast database
ASP.NET Programming with C# and SQL Server, First Edition

43. 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
ASP.NET Programming with C# and SQL Server, First Edition

44. Retrieving Records (cont’d.)
Figure 7-13 Individual fields returned with a SELECT statement
ASP.NET Programming with C# and SQL Server, First Edition

45. 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)
ASP.NET Programming with C# and SQL Server, First Edition

46. Sorting Query Results (cont’d.)
Figure 7-14 Results returned from inventory table of the skateboards database sorted by price
ASP.NET Programming with C# and SQL Server, First Edition

47. Sorting Query Results (cont’d.)
Figure 7-15 Results returned from inventory table of the skateboards database reverse sorted by price
ASP.NET Programming with C# and SQL Server, First Edition

48. 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
ASP.NET Programming with C# and SQL Server, First Edition

49. 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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50. 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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51. 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
ASP.NET Programming with C# and SQL Server, First Edition

52. 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
ASP.NET Programming with C# and SQL Server, First Edition

53. 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
ASP.NET Programming with C# and SQL Server, First Edition

54. 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
ASP.NET Programming with C# and SQL Server, First Edition

55. 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
ASP.NET Programming with C# and SQL Server, First Edition

56. 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
ASP.NET Programming with C# and SQL Server, First Edition

57. 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
ASP.NET Programming with C# and SQL Server, First Edition

58. 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
ASP.NET Programming with C# and SQL Server, First Edition