1. Concepts of Database Management Sixth Edition
Chapter 3
The Relational Model 2: SQL

2. Objectives Introduce Structured Query Language (SQL)
Use simple and compound conditions in SQL
Use computed fields in SQL
Use built-in SQL functions
Use subqueries in SQL
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3. Objectives (continued)
Group records in SQL
Join tables using SQL
Perform union operations in SQL
Use SQL to update database data
Use an SQL query to create a table in a database
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4. Introduction SQL (Structured Query Language)
Allows users to query a relational database
Must enter commands to obtain the desired results
Standard language for relational database manipulation
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5. Getting Started with SQL
If you are completing the work in this chapter using Microsoft Office Access 2003, Microsoft Office Access 2007, or MySQL version 4.1 or higher, the following sections contain specific information about your DBMS
Concepts of Database Management

6. Getting Started with Microsoft Office Access 2003 and 2007
If you are using the Access 2003 or 2007 version of the Premiere Products database provided with the Data Files for this text:
Tables in the database have already been created
You will not need to execute the CREATE TABLE commands to create the tables or the INSERT commands to add records to the tables
Concepts of Database Management

7. Getting Started with Microsoft Office Access 2003 and 2007 (continued)
To execute the SQL commands shown in the figures in Access 2003
Open the Premiere Products database
Click Queries on the Objects bar in the Database window, and then double-click the “Create query in Design view” option
Click the Close button in the Show Table dialog box
Click the View button list arrow on the Query Design toolbar, and then click SQL View
The query opens in SQL view, ready for you to type your SQL commands
Concepts of Database Management

8. Getting Started with Microsoft Office Access 2003 and 2007 (continued)
To execute SQL commands shown in the figures in Access 2007:
Open the Premiere Products database
Click the Create tab on the Ribbon
Click the Query Design button in the Other group
Click the Close button in the Show Table dialog box
Click the View button arrow in the Results group on the Query Design Tools tab, then click SQL View
The Query1 tab displays the query in SQL view, ready for you to type your SQL commands
Concepts of Database Management

9. Getting Started with MySQL
MySQL-Premiere script provided with the Data Files for this text will:
Activate the database
Create the tables
Insert the records
To run a script in MySQL:
Type the SOURCE command followed by the name of the file
Press the Enter key
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10. Getting Started with MySQL (continued)
Before typing commands in MySQL, you must activate the database by typing the USE command followed by the name of the database
The most recent command entered in MySQL is stored in a special area of memory called the statement history
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11. Table Creation SQL CREATE TABLE command
Creates a table by describing its layout
Typical restrictions placed on table and column names by DBMS
Names cannot exceed 18 characters
Names must start with a letter
Names can contain only letters, numbers, and underscores (_)
Names cannot contain spaces
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12. Table Creation (continued)
INTEGER
Numbers without a decimal point
SMALLINT
Uses less space than INTEGER
DECIMAL(p,q)
P number of digits; q number of decimal places
CHAR(n)
Character string n places long
DATE
Dates in DD-MON-YYYY or MM/DD/YYYY form
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13. Simple Retrieval SELECT-FROM-WHERE: SQL retrieval command
SELECT clause: lists fields to display
FROM clause: lists table or tables that contain data to display in query results
WHERE clause (optional): lists any conditions to be applied to the data to retrieve
Simple condition: field name, a comparison operator, and either another field name or a value
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14. Simple Retrieval (continued)
FIGURE 3-5: SQL query with WHERE condition
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15. Simple Retrieval (continued)
FIGURE 3-6: Query results
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16. Simple Retrieval (continued)
FIGURE 3-7: Comparison operators used in SQL commands
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17. Compound Conditions Compound condition
Connecting two or more simple conditions using one or both of the following operators: AND and OR
Preceding a single condition with the NOT operator
Connecting simple conditions using AND operator
All of the simple conditions must be true for the compound condition to be true
Connecting simple conditions using OR operator
Any of the simple conditions must be true for the compound condition to be true
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18. Compound Conditions (continued)
FIGURE 3-14: Compound condition that uses the AND operator
FIGURE 3-15: Query results
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19. Compound Conditions (continued)
FIGURE 3-16: Compound condition that uses the OR operator
FIGURE 3-17: Query results
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20. Compound Conditions (continued)
Preceding a condition by NOT operator
Reverses the truth or falsity of the original condition
BETWEEN operator
Value must be between the listed numbers
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21. Computed Fields Computed field or calculated field
Field whose values you derive from existing fields
Can involve:
Addition (+)
Subtraction (-)
Multiplication (*)
Division (/)
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22. Computed Fields (continued)
FIGURE 3-24: SQL query with a computed field and condition
FIGURE 3-25: Query results
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23. Using Special Operators (LIKE and IN)
Wildcards in Access SQL
Asterisk (*): collection of characters
Question mark (?): any individual character
Wildcards in MySQL
Percent sign (%): any collection of characters
Underscore (_): any individual character
To use a wildcard, include the LIKE operator in the WHERE clause
IN operator provides a concise way of phrasing certain conditions
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24. Using Special Operators (LIKE and IN) (continued)
FIGURE 3-26: SQL query with a LIKE operator
FIGURE 3-27: Query results
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25. Using Special Operators (LIKE and IN) (continued)
FIGURE 3-28: SQL query with an IN operator
FIGURE 3-29: Query results
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26. Sorting Sort data using the ORDER BY clause
Sort key: field on which to sort data
When sorting data on two fields:
Major sort key (or primary sort key): more important sort key
Minor sort key (or secondary sort key): less important sort key
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27. Sorting (continued) Concepts of Database Management
FIGURE 3-32: SQL query to sort data on multiple fields
FIGURE 3-33: Query results
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28. Built-in Functions Built-in functions (aggregate functions) in SQL
COUNT: calculates number of entries
SUM or AVG: calculates sum or average of all entries in a given column
MAX or MIN: calculates largest or smallest values respectively
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29. Built-in Functions (continued)
FIGURE 3-34: SQL query to count records
FIGURE 3-35: Query results
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30. Subqueries Subquery: inner query Subquery is evaluated first
Outer query is evaluated after the subquery
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31. Subqueries (continued)
FIGURE 3-40: SQL query with a subquery
FIGURE 3-41: Query results
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32. Grouping Create groups of records that share a common characteristic
GROUP BY clause indicates grouping in SQL
HAVING clause is to groups what the WHERE clause is to rows
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33. Grouping (continued) Concepts of Database Management
FIGURE 3-44: SQL query to restrict the groups that are included
FIGURE 3-45: Query results
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34. Joining Tables Queries can locate data from more than one table
Enter appropriate conditions in the WHERE clause
To join tables, construct the SQL command as:
SELECT clause: list all fields you want to display
FROM clause: list all tables involved in the query
WHERE clause: give the condition that will restrict the data to be retrieved to only those rows from the two tables that match
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35. Joining Tables (continued)
FIGURE 3-48: SQL query to join tables
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36. Joining Tables (continued)
FIGURE 3-49: Query results
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37. Union
Union of two tables is a table containing all rows in the first table, the second table, or both tables
Two tables involved must be union compatible
Same number of fields
Corresponding fields must have same data types
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38. FIGURE 3-54: SQL query to perform a union FIGURE 3-55: Query results
Union (continued)
FIGURE 3-54: SQL query to perform a union
FIGURE 3-55: Query results
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39. Updating Tables UPDATE command makes changes to existing data
INSERT command adds new data to a table
DELETE command deletes data from the database
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40. Updating Tables (continued)
FIGURE 3-56: SQL query to update data
FIGURE 3-57: SQL query to insert a row
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41. Updating Tables (continued)
FIGURE 3-58: SQL query to delete rows
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42. Creating a Table from a Query
INTO clause
Saves the results of a query as a table
Specified before FROM and WHERE clauses
MySQL
Create the new table using a CREATE TABLE command
Use an INSERT command to insert the appropriate data into the new table
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43. Creating a Table from a Query (continued)
FIGURE 3-59a: Query to create a new table (Access)
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44. Creating a Table from a Query (continued)
FIGURE 3-59b: Query to create a new table (MySQL)
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45. Summary of SQL Commands
Generic versions of SQL commands for every example presented in this chapter
In most cases, commands in Access are identical to the generic versions
For those commands that differ, both the generic version and the Access version are included
Concepts of Database Management

46. Summary
Structured Query Language (SQL) is a language that is used to manipulate relational databases
Basic form of an SQL query: SELECT-FROM-WHERE
Use CREATE TABLE command to describe table layout to the DBMS, which creates the table
In SQL retrieval commands, fields are listed after SELECT, tables are listed after FROM, and conditions are listed after WHERE
In conditions, character values must be enclosed in single quotation marks
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47. Summary (continued)
Compound conditions are formed by combining simple conditions using either or both of the following operators: AND and OR
Sorting is accomplished using ORDER BY clause
When the data is sorted in more than one field, can have a major and minor sort keys
Grouping: use the GROUP BY clause
HAVING clause: restricts the rows to be displayed
Concepts of Database Management

48. Summary (continued)
Joining tables: use a condition that relates matching rows in the tables to be joined
Built-in (aggregate) functions: COUNT, SUM, AVG, MAX, and MIN
One SQL query can be placed inside another; the subquery is evaluated first
UNION operator: unifies the results of two queries
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49. Summary (continued)
Calculated fields: include the calculation, the word AS, the name of the calculated field
INSERT command adds a new row to a table
UPDATE command changes existing data
DELETE command deletes records
INTO clause is used in a SELECT command to create a table containing the results of the query
Concepts of Database Management