Lesson01 学会使用基本的SQL语句

Oracle OCP 考试系列培训
之
1Z0-007 Lesson1
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1-1 Copyright © 2011, www.OracleOnLinux.cn . Part rights reserved.

1
Retrieving Data Using
the SQL SELECT Statement

1-2 Copyright © 2011, www.OracleOnLinux . Part rights reserved.
OracleOnLinux
OracleOnLinux.cn

Objectives

After completing this lesson, you should be able to do
the following:
• List the capabilities of SQL SELECT statements
• Execute a basic SELECT statement
• Differentiate between SQL statements and
iSQL*Plus commands
SQL*


Lesson Agenda

• Basic SELECT statement
• Arithmetic expressions and NULL values in the
SELECT statement
• Column aliases
• Use of concatenation operator, literal character strings,
alternative quote operator, and the DISTINCT keyword
• DESCRIBE command


Capabilities of SQL SELECT Statements

Projection Selection

Table 1 Table 1

Join

Table 1 Table 2


Basic SELECT Statement

SELECT *|{[DISTINCT] column|expression [alias],...}
FROM table;

• SELECT identifies the columns to be displayed
• FROM identifies the table containing those columns


Selecting All Columns

SELECT *
FROM departments;


Selecting Specific Columns

SELECT department_id, location_id
FROM departments;


Writing SQL Statements

• SQL statements are not case-sensitive.
• SQL statements can be on one or more lines.
• Keywords cannot be abbreviated or split
across lines.
• Clauses are usually placed on separate lines.
• Indents are used to enhance readability.
• In iSQL*Plus, SQL statements can optionally be
SQL*
terminated by a semicolon (;). Semicolons are
required if you execute multiple SQL statements.
• In SQL*plus, you are required to end each SQL
SQL*
statement with a semicolon (;).


Column Heading Defaults

• iSQL*Plus:
SQL*
– Default heading alignment: Center
– Default heading display: Uppercase
• SQL*Plus:
SQL*
– Character and Date column headings are
Left- aligned
– Number column headings are right-aligned
– Default heading display: Uppercase


Arithmetic Expressions

Create expressions with number and date data by
using arithmetic operators.
Operator Description
+ Add
- Subtract
* Multiply
/ Divide


Using Arithmetic Operators

SELECT last_name, salary, salary + 300
FROM employees;

…


Operator Precedence

SELECT last_name, salary, 12*salary+100
12*
FROM employees; 1

…
SELECT last_name, salary, 12*(salary+100)
12*
FROM employees; 2

…


Defining a Null Value

• A null is a value that is unavailable, unassigned,
unknown, or inapplicable.
• A null is not the same as a zero or a blank space.
SELECT last_name, job_id, salary, commission_pct
FROM employees;

…

…


Null Values
in Arithmetic Expressions

Arithmetic expressions containing a null value
evaluate to null.
SELECT last_name, 12*salary,12*salary*(1+commission_pct)
12* 12* salary*
FROM employees;

…

…


Defining a Column Alias

A column alias:
• Renames a column heading
• Is useful with calculations
• Immediately follows the column name (There can
also be the optional AS keyword between the
column name and alias.)
• Requires double quotation marks if it contains
spaces or special characters or if it is case-
sensitive
• Can not be used in Where clause


Using Column Aliases

SELECT last_name AS name, commission_pct comm
FROM employees;

…

SELECT last_name "Name" , salary*12 "Annual Salary"
salary*
FROM employees;

…


Concatenation Operator

A concatenation operator:
• Links columns or character strings to other
columns
• Is represented by two vertical bars (||)
• Creates a resultant column that is a character
expression
SELECT last_name||job_id AS "Employees"
FROM employees;

…


Concatenation Operator

SELECT last_name||'''s'||salary
FROM employees;

SELECT last_name||chr(39)||'s'||salary
FROM employees;

SELECT ASCII('''')
FROM dual;

SELECT ASCII('?')
FROM dual;


Literal Character Strings

• A literal is a character, a number, or a date that is
included in the SELECT statement.
• Date and character literal values must be enclosed
by single quotation marks.
• Each character string is output once for each
row returned.


Using Literal Character Strings

SELECT last_name ||' is a ' ||job_id
AS "Employee Details"
FROM employees;

…


Duplicate Rows

The default display of queries is all rows, including
duplicate rows.
SELECT department_id
FROM employees; 1

…
SELECT DISTINCT department_id
FROM employees; 2

…


SQL and iSQL*Plus Interaction
SQL*

SQL statements
Oracle
server
Internet
browser

iSQL*Plus
SQL* Query results
commands

Formatted report
Client


SQL Statements Versus
iSQL*Plus Commands
SQL*
SQL iSQL*Plus
SQL*
• A language • An environment
• ANSI standard • Oracle-proprietary
• Keyword cannot be • Keywords can be
abbreviated abbreviated
• Statements manipulate • Commands do not allow
data and table definitions manipulation of values in
in the database the database
• Runs on a browser
• Centrally loaded; does not
have to be implemented
on each machine

SQL iSQL*Plus
SQL*
statements commands


Overview of iSQL*Plus
SQL*

After you log in to iSQL*Plus, you can:
SQL*
• Describe table structures
• Enter, execute, and edit SQL statements
• Save or append SQL statements to files
• Execute or edit statements that are stored in
saved script files


Logging In to iSQL*Plus
SQL*

From your browser environment:


iSQL*Plus Environment
SQL*
8 9

7

1
6

2 3 4 5


Displaying Table Structure

Use the iSQL*Plus DESCRIBE command to display the
SQL*
structure of a table:

DESC[RIBE] tablename


Displaying Table Structure

DESCRIBE employees


Interacting with Script Files

SELECT last_name, hire_date, salary
FROM employees; 1

2



1



D:TEMPemp_data.sql

2
3


iSQL*Plus History Page
SQL*

3

2

1


iSQL*Plus History Page
SQL*

3

4


Setting iSQL*Plus Preferences
SQL*

1

2
3


Setting the Output Location Preference
2

1


Summary

In this lesson, you should have learned how to:
• Write a SELECT statement that:
– Returns all rows and columns from a table
– Returns specified columns from a table
– Uses column aliases to display more descriptive
column headings
• Use the iSQL*Plus environment to write, save, and
SQL*
execute SQL statements and iSQL*Plus
SQL*
commands
SELECT *|{[DISTINCT] column|expression [alias],...}
FROM table;


Practice 1: Overview

This practice covers the following topics:
• Selecting all data from different tables
• Describing the structure of tables
• Performing arithmetic calculations and specifying
column names
• Using iSQL*Plus
SQL*


Practice 1

Q1: A SELECT statement can be used to perform these
three functions:
1. Choose rows from a table.
2. Choose columns from a table.
3. Bring together data that is stored in different tables by
creating a link between them.
Which set of keywords describes these capabilities?
A. difference, projection, join
B. selection, projection, join
C. selection, intersection, join
D. intersection, projection, join
E. difference, projection, product


Practice 1

Q2: Evaluate this SQL statement:

SELECT e.EMPLOYEE_ID,e.LAST_NAME,
e.DEPARTMENT_ID, d.DEPARTMENT_NAME
FROM EMPLOYEES e, DEPARTMENTS d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID;

In the statement, which capabilities of a SELECT statement are
performed?
A. selection, projection, join
B. difference, projection, join
C. selection, intersection, join
D. intersection, projection, join
E. difference, projection, product


Practice 1

Q3: Evaluate this SQL statement:

SELECT ename, sal, 12 *sal+100
12*
FROM emp;

The SAL column stores the monthly salary of the employee.
Which change must be made to the above syntax to calculate
the annual compensation as "monthly salary plus a monthly
bonus of $100, multiplied by 12"?
A. No change is required to achieve the desired results.
B. SELECT ename, sal, 12 *(sal+100) FROM emp;
12*
C. SELECT ename, sal, (12 *sal)+100 FROM emp;
(12*
D. SELECT ename, sal+100, *12 FROM emp;
sal+100,*


Practice 1

Q4: Which SQL statement generates the alias Annual
Salary for the calculated column SALARY *12?
SALARY*

A. SELECT ename, salary *12 'Annual Salary'
salary*
FROM employees;
B. SELECT ename, salary *12 "Annual Salary"
salary*
FROM employees;
C. SELECT ename, salary *12 AS Annual Salary
salary*
FROM employees;
D. SELECT ename, salary *12 AS INITCAP("ANNUAL
salary*
SALARY")
FROM employees


Practice 1

Q5: The CUSTOMERS table has these columns:

CUSTOMER_ID NUMBER(4) NOT NULL
CUSTOMER_NAME VARCHAR2(100) NOT NULL
CUSTOMER_ADDRESS VARCHAR2(150)
CUSTOMER_PHONE VARCHAR2(20)

You need to produce output that states "Dear Customer
customer_name, ".
The customer_name data values come from the
CUSTOMER_NAME column in the CUSTOMERS table.
Which statement produces this output?


Practice 1

A. SELECT dear customer, customer_name,
FROM customers;
B. SELECT "Dear Customer", customer_name || ','
FROM customers;
C. SELECT 'Dear Customer ' || customer_name ','
FROM customers;
D. SELECT 'Dear Customer ' || customer_name || ','
FROM customers;
E. SELECT "Dear Customer " || customer_name || ","
FROM customers;
F. SELECT 'Dear Customer ' || customer_name || ',' ||
FROM customers;


Practice 1

Q6: Which two are attributes of iSQL *Plus? (Choose two.)
iSQL*

A. iSQL*Plus commands cannot be abbreviated.
iSQL*
B. iSQL*Plus commands are accessed from a browser.
iSQL*
C. iSQL*Plus commands are used to manipulate data in
iSQL*
tables.
D. iSQL*Plus commands manipulate table definitions in
iSQL*
the database.
E. iSQL*Plus is the Oracle proprietary interface for
iSQL*
executing SQL statements.


Lesson01 学会使用基本的SQL语句

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