1 Introduction to SQL
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Transcript of 1 Introduction to SQL
8/8/2019 1 Introduction to SQL
http://slidepdf.com/reader/full/1-introduction-to-sql 1/13
SQL
Introduction
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Key Terms
Data ± Any important information like an employee¶s salar y.
Database
± An organized collection of data or information.
DBMS ± Database Management System
± A Program that stor es, r etrieves, modifies data in
database. Relational database
± Collection of two-dimensional tables.
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Relational Database Components
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How a database is cr eated?
Model of
system
in client¶s
mind
Entity model of
client¶s model
Tables on disk
Oracle
server
Table modelof entity model
Entity becomes a table
Attribute becomes columns of a table
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ER Diagram
± ER model consists of the various entities in a business and the r elationships among them.
± Scenario:
³. . . Assign one or mor e employees to a
department . . .´
³. . . Some departments do not yet have assigned
employees«.´
EMPLOYEE
#* number
* name
o job title
DEPARTMENT
#* number
* nameo location
assigned to
composed of
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Relating Multiple Tables
± Each row of data in a table is uniquely identified by a
primar y key.
± You can logically r elate data from multiple tables
using for eign keys.
Table name: EMPLOYEES
Table name:D
EPARTMENTS
Primary key Primary keyForeign key
«
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Relational Database Terminology
1
23
4
6
5
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Using SQL to Quer y Your
Database Structur ed quer y language (SQL) is:
± The ANSI standard language for operating
r elational databases
± Efficient, easy to learn, and use ± Functionally complete (With SQL, you can define,
r etrieve, and manipulate data in the tables.)
SELECT department_name
FROM departments;Oracle
server
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Cr eateReadUpdateDelete
Update:update xxx_ temp
set id = 4
wher e id < 10
Delete:
delete from xxx_ temp
wher e id < 10
Cr eate:insert into xxx_ temp
values (2, 'Test 2');
Read:select id, text
from xxx_ temp
wher e id < 10
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SQL Statements
SELECTINSERT
UPDATE
DELETE
MERGE
CREATE
ALTER
DROP
RENAME
TRUNCATE
COMMENT
GRANT
REVOKE
COMMIT
ROLLBACK
SAVEPOINT
Data manipulation
language (DML)
Data definition language
(DDL)
Transaction control
Data control language (DCL)
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Oracle 9i Components
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(HR) Schema generally used for
training
DEPARTMENTSdepartment_id
department _ namemanager _ idlocation _ id
LOCATIONSlocation_id
str eet _ addr esspostal_ code
citystate_ province
countr y_ id
COUNTRIEScountry_id
countr y_ namer egion _ id
REGIONSregion_id
r egion _ name
EMPLOYEESemployee_id
first _ namelast _ name
phone_ number hir e_ date job _ idsalar y
commission _ pctmanager _ id
department _ id
JOBS job_id
job _ titlemin _ salar ymax_ salar y
JOB_HISTORYemployee_id
start_date
end _ date
job _ id
department _ id
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Key Points For SQL Statements
SQL statements ar e not case-sensitive. The data enter ed is case sensitive.
SQL statements can be enter ed on one or many lines.
Keywords cannot be split across lines or abbr eviated.
Clauses ar e usually placed on separate lines for r eadability
and ease of editing. Indents should be used to make code mor e r eadable.
Keywords typically ar e enter ed in uppercase; all other words, such as table names and columns names ar eenter ed in lowercase.
Null is a value that is unavailable, unassigned, unknown, or inapplicable. Null is not the same as zero or a blank space.Zero is a number and blank space is a character .
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 within single quotation marks.