Download Structure Query Language

SI 654
Database Application Design
Winter 2003
Dragomir R. Radev
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Database Processing
Eighth Edition
Structured
Query
Language
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Chapter 9
David M. Kroenke
© 2002 by Prentice Hall
Structure Query Language
• Structure Query Language is known
as either
– Its acronym, SQL, or
– SEQUEL, the name of the original
version of SQL
• SEQUEL was developed by IBM in
the mid-1970s.
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SQL, not a Procedural
Programming Language
• SQL is not a programming language
itself, it is a data access language
• SQL may be embedded in traditional
procedural programming languages
(like COBOL)
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SQL Syntax
SQL is not case sensitive.
SELECT field(s) ‘what columns will be
retrieved
FROM table(s); ‘which table contains the
column data
e.g.,
SELECT Name, Phone
FROM Student;
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The DISTINCT Qualifier
• Eliminating duplicate rows on the
output…
SELECT DISTINCT StateAddress
FROM Employee;
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The WHERE Clause
• Reducing the output based on
specified criteria…
SELECT StudentName
FROM Students
WHERE GradePointAverage >= 3.0;
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Comparison Operators
Equals =
Not equals <>
Greater than >
Less than <
Greater than or equal to >=
Less than or equal to <=
Within a list of values IN
A logical NOT
Within a range BETWEEN
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IN a List of Values
SELECT StudentName
FROM Student
WHERE State IN [‘PA’, ‘MA’, ‘CA’];
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The Logical NOT
SELECT StudentName
FROM Students
WHERE State NOT IN [‘NJ’, ‘NM’, ‘NY’];
SELECT StudentName
FROM Students
WHERE NOT GradePointAverage >= 3.0;
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Within a Range of Values
SELECT StudentName
FROM Student
WHERE StudentID BETWEEN 250 and 300;
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Using Wildcard Character
Substitutions
• The LIKE keyword is used in place of
the = sign when you use wildcard
characters.
• The underscore character (_) is a
single character substitution
• The percent character (%) is a multicharacter substitution
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Using LIKE
SELECT StudentID
FROM Student
WHERE StudentName LIKE ‘K%’;
SELECT PartName
FROM Part
WHERE PartNumber LIKE ‘_ABC%’;
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NULL Means Nothing
• A NULL character means that nothing
has been entered. This is different
from a space or a zero.
SELECT Name
FROM Student
WHERE Major IS NULL;
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ORDER BY… Sorting Outputs
• Sorting in descending order…
SELECT StudentID, Name
FROM Student
ORDER BY Name DESC;
• Sorting in ascending order…
SELECT StudentID, Name
FROM Student
ORDER BY Name ASC;
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Built-in Functions
•
•
•
•
Counting number of rows COUNT
Adding the values in a column SUM
Averaging the values in a column AVG
Finding the maximum value in a column
MAX
• Finding the minimum value in a column MIN
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Built-in Functions
SELECT Count (*)
FROM Student
WHERE State = ‘WI’;
SELECT Sum (Amount)
FROM SalesReceipt;
SELECT Max (Score)
FROM Assignments;
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Grouping the Output
SELECT Name, State
FROM Student
GROUP BY State;
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Reducing the Groups
Displayed
SELECT Name, State
FROM Student
GROUP BY State
HAVING Count (*) > 4;
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Sub-Queries
SELECT Name
FROM Student
WHERE SID IN
(SELECT StudentNumber
FROM Enrollment
WHERE ClassName = ‘MIS445’);
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Joining Tables
SELECT Student.SID, Student.Name,
Enrollment.ClassName
FROM Student, Enrollment
WHERE Student.SID =
Enrollment.StudentNumber AND
Student.State = ‘OH’;
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EXISTS
SELECT DISTINCT StudentNumber
FROM Enrollment A
WHERE EXISTS
(SELECT *
FROM Enrollment B
WHERE A.StudentNumber =
B.StudentNumber
AND A.ClassName NOT = B.ClassName);
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Entering Data
INSERT INTO Enrollment
VALUES (400, ‘MIS445’, 44);
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Deleting Data
DELETE Student
WHERE Student.SID = 100;
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Modifying Data
UPDATE Enrollment
SET SeatNumber = 44
WHERE SID = 400;
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