Oracle 10g SQL Fundamentals I-Les01

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Retrieving Data Using the SQL SELECT Statement : 

Retrieving Data Using the SQL SELECT Statement

Objectives : 

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

Capabilities of SQL SELECT Statements : 

Capabilities of SQL SELECT Statements Selection Projection Table 1 Table 2 Table 1 Table 1 Join

Basic SELECT Statement : 

Basic SELECT Statement SELECT identifies the columns to be displayed FROM identifies the table containing those columns SELECT *|{[DISTINCT] column|expression [alias],...} FROM table;

Selecting All Columns : 

Selecting All Columns SELECT * FROM departments;

Selecting Specific Columns : 

Selecting Specific Columns SELECT department_id, location_id FROM departments;

Writing SQL Statements : 

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

Column Heading Defaults : 

Column Heading Defaults iSQL*Plus: Default heading alignment: Center Default heading display: Uppercase SQL*Plus: Character and Date column headings are left- aligned Number column headings are right-aligned Default heading display: Uppercase

Arithmetic Expressions : 

Arithmetic Expressions Create expressions with number and date data by using arithmetic operators.

Using Arithmetic Operators : 

SELECT last_name, salary, salary + 300 FROM employees; Using Arithmetic Operators

Operator Precedence : 

SELECT last_name, salary, 12*salary+100 FROM employees; Operator Precedence SELECT last_name, salary, 12*(salary+100) FROM employees; 1 2

Defining a Null Value : 

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 : 

SELECT last_name, 12*salary*commission_pct FROM employees; Null Values in Arithmetic Expressions Arithmetic expressions containing a null value evaluate to null. … …

Defining a Column Alias : 

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

Using Column Aliases : 

Using Column Aliases SELECT last_name "Name" , salary*12 "Annual Salary" FROM employees; SELECT last_name AS name, commission_pct comm FROM employees; … …

Concatenation Operator : 

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;

Literal Character Strings : 

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 eachrow returned.

Using Literal Character Strings : 

Using Literal Character Strings … SELECT last_name ||' is a '||job_id AS "Employee Details" FROM employees;

Alternative Quote (q) Operator : 

Alternative Quote (q) Operator Specify your own quotation mark delimiter Choose any delimiter Increase readability and usability SELECT department_name || q'[, it's assigned Manager Id: ]' || manager_id AS "Department and Manager" FROM departments; …

Duplicate Rows : 

Duplicate Rows The default display of queries is all rows, including duplicate rows. SELECT department_id FROM employees; SELECT DISTINCT department_id FROM employees; … 1 2

SQL and iSQL*Plus Interaction : 

SQL and iSQL*Plus Interaction SQL statements Query results iSQL*Plus commands Client Formatted report Internet browser

SQL Statements Versus iSQL*Plus Commands : 

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

Overview of iSQL*Plus : 

Overview of iSQL*Plus After you log in to iSQL*Plus, you can: 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 : 

Logging In to iSQL*Plus From your browser environment:

iSQL*Plus Environment : 

iSQL*Plus Environment 6 3 4 5 1 2 8 9 7

Displaying Table Structure : 

Displaying Table Structure Use the iSQL*Plus DESCRIBE command to display the structure of a table: DESC[RIBE] tablename

Displaying Table Structure : 

Displaying Table Structure DESCRIBE employees

Interacting with Script Files : 

Interacting with Script Files SELECT last_name, hire_date, salary FROM employees; 1 2

Interacting with Script Files : 

Interacting with Script Files

Interacting with Script Files : 

Interacting with Script Files 1

Interacting with Script Files : 

Interacting with Script Files 2 3 D:\TEMP\emp_data.sql

iSQL*Plus History Page : 

iSQL*Plus History Page 1 2 3

iSQL*Plus History Page : 

iSQL*Plus History Page 3 4

Setting iSQL*Plus Preferences : 

Setting iSQL*Plus Preferences 2 3 1

Setting the Output Location Preference : 

Setting the Output Location Preference 1 2

Summary : 

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 execute SQL statements and iSQL*Plus commands SELECT *|{[DISTINCT] column|expression [alias],...} FROM table;

Practice 1: Overview : 

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

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