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International Islamic University MalaysiaDepartment of Information Systems
Kulliyyah of Information & Communication Technology
LECTURE 4: BASIC SELECT STATEMENTS
Dr. Mira Kartiwi
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Capabilities of SQL SELECT Statements
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Selection (Restriction) – Allows for the retrieval of rows that satisfy certain specified condition (predicate).
Projection – Allows for the retrieval of specified columns (attributes).
Joining – Allows for the linking of data in different tables.
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More About SELECT
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT is technically a Data Manipulation Language (DML). However, Oracle does not classify it as such.
You can write SELECT statements on multiple lines. However, you are not allowed to split or abbreviate keywords.
SELECT statements are not case sensitive.
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More About SELECT
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Clauses are usually placed on separate lines.
Indents are used to enhance readability.
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Basic SELECT Statement
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT *| { [DISTINCT] column | expression[alias],...}FROM table;
SELECT identifies what column FROM identifies which table
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Selecting All Columns
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT *FROM doctor;
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Selecting Specific Columns
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name, areaFROM doctor;
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Using Arithmetic Operations
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name, (annual_bonus+ 500)FROM doctor; Four arithmetic operations according to
precedence: (*, /), (+, -)
Operators of the same priority are evaluated from left to right.
Parentheses are used to force prioritized evaluation and to clarify statements.
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Operator Precedence and Parantheses
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name, annual_bonus, 10*annual_bonus+500 FROM doctor;
SELECT doc_name, annual_bonus, 10*(annual_bonus+500) FROM doctor;
--What is the difference????
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NULL Values
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
How many doctor has Null value in the result???Why??
Arithmetic expressions containing a null value evaluate to null
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Column Alias
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Renames a column heading. Useful with calculations. Immediately follows the column name – there can
also be the optional AS keyword between column name and alias.
Requires double quotation marks if it contains spaces or special characters or is case sensitive.
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Column Alias
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name AS name, annual_bonusFROM doctor
SELECT doc_name AS “Name”, annual_bonus AS “Bonus”FROM doctor
SELECT doc_name, annual_bonus AS “Bonus Upgrade”FROM doctor
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Concatenation Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name||area AS “Doctor”FROM doctor; Concatenates columns or character
strings to other columns. Is represented by two vertical bars (||). Creates a resultant column that is a
character expression.
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Literal Character String
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name || ' is from ' || area AS “DOCTOR”FROM doctor; A literal is a character, a number, or a date
included in the SELECT statement. Date and character literal values must be
enclosed within single quotation marks. Each character string is output once for each row
returned.
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Eliminating Duplicate Rows
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT DISTINCT areaFROM doctor;
-- how many area??????
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Limiting the Rows Selected
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT *| { [DISTINCT] column | expression[alias],...}
FROM tableWHERE condition(s);
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The Where Clause
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
The WHERE clause can be added to the SELECT statement to restrict the results to rows that satisfy a specified condition.
Rows that do not meet the condition will not be included in the results.
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Comparisons
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
The two expressions must be of the same type
Character string literals should be enclosed in single quotes
Date literals should be of the form 'DD-MON-YY'
Numeric literals should consist of digits and optionally, a decimal and/or sign (no commas or dollar signs)
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Comparison Conditions
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Equal (=) Greater than (>) Greater than or equal to (>=) Less than (<) Less than or equal to (<=) Not equal to (<>, !=, ^=)
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WHERE Clause
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_nameFROM doctorWHERE chgperappt >= 40;
--What does it means????? -- how many doctor name James????? -- What area is Stevenson?????
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Other Comparison Conditions
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Between two values (inclusive) –BETWEEN... AND...
IN (set) LIKE IS NULL IS NOT NULL
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BETWEEN Condition
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Several special operators serve as shortcuts for longer expressions.One is the BETWEEN operator.
It is used to determine whether or not a value lies within a specific range (including the end points)
General syntax:Expression1 BETWEEN Expression2 ANDExpression 3
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BETWEEN Condition
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_name, annual_bonusFROM doctorWHERE annual_bonus BETWEEN 2000 AND 4000;
-- how many people?
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The IN Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Used to see if a value occurs in a set of possible values
The set of possible values is specified within parentheses with commas between values
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IN Condition
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT doc_id, doc_name, areaFROM doctorWHERE doc_id IN (100,356, 558);
-- what area are they in???????
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The IS NULL Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Any comparison to a null value that uses the standard comparison operators will not yield a match.
If a check for null values is needed, the IS NULL operator must be used.
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The IS NULL Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Display the IDs of doctors that do not receive annual bonuses.
SELECT doc_idFROM doctorWHERE annual_bonus IS NULL;
--What is the name?---
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The LIKE Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Used in conjunction with wildcard characters to match character string patterns
% is used to match zero or more characters
_ is used to match a single character Wildcards cannot be used without the
LIKE operator The LIKE operator should not be used
without wildcards
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LIKE Condition
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT *FROM doctorWHERE doc_name LIKE 'J%';-- change to lowercase j
Note:– Represents any sequence of zero or more
characters (%)– Represents a single character (_)
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The LIKE Operator
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Display the full name and phone number for customers whose phone number begins with 549-67SELECT pt_lname || ', ' || pt_fname "FULL NAME"FROM patientWHERE ptdob LIKE ’13-MAY-__' ;
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Logical Operators
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
3 standard logical operators (AND, OR, andNOT) are used to combine expressions
AND will return a value of true only if both expressions are true
OR will return a value of true if either or both of the expressions are true
NOT will return the opposite value of the expression.
Order of precedence: NOT, AND, OR
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Other NOT Operators
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
The NOT operator can also be used in conjunction with the special operators as follows: NOT BETWEEN NOT IN IS NOT NULL NOT LIKE
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NULL and NOT NULL Conditions
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
SELECT docid, docname, annual_bonus FROM doctor WHERE annual_bonus IS NULL;
TO NEGATE ..
SELECT docid, docname, annual_bonus FROM doctor WHERE annual_bonus IS NOT NULL;
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Lab Assignment 1
International Islamic University Malaysia Kuliyyah of ICT – Department of Information Systems
Run the hospital script and create a question in English as well as its SQL query that generates: NULL values Values not within a specific range List of names that started from or ended
with specific letter