SQL Inteoduction to SQL manipulating of data

Introduction toIntroduction to
SQLSQL
Manipulation ofManipulation of
DataData
2

OverviewOverview
• Define a database using SQL data definition
language
• Work with Views
• Write single table queries
• Establish referential integrity
3

SQL OverviewSQL Overview
• Structured Query Language
• The standard for relational database
management systems (RDBMS)
• SQL-92 and SQL-99 Standards – Purpose:
o Specify syntax/semantics for data definition and
manipulation
o Define data structures
o Enable portability
o Specify minimal (level 1) and complete (level 2)
standards
o Allow for later growth/enhancement to standard
4

SQL EnvironmentSQL Environment
• Catalog
o A set of schemas that constitute the description of a
database
• Schema
o The structure that contains descriptions of objects created by
a user (base tables, views, constraints)
• Data Definition Language (DDL)
o Commands that define a database, including creating,
altering, and dropping tables and establishing constraints
• Data Manipulation Language (DML)
o Commands that maintain and query a database
• Data Control Language (DCL)
o Commands that control a database, including administering
privileges and committing data
6

SQL Data typesSQL Data types
(from Oracle 9i)(from Oracle 9i)
• String types
o CHAR(n) – fixed-length character data, n characters long
Maximum length = 2000 bytes
o VARCHAR2(n) – variable length character data, maximum 4000
bytes
o LONG – variable-length character data, up to 4GB. Maximum 1
per table
• Numeric types
o NUMBER(p,q) – general purpose numeric data type
o INTEGER(p) – signed integer, p digits wide
o FLOAT(p) – floating point in scientific notation with p binary digits
precision
• Date/time type
o DATE – fixed-length date/time in dd-mm-yy form
7

SQL Database DefinitionSQL Database Definition
• Data Definition Language (DDL)
• Major CREATE statements:
o CREATE SCHEMA – defines a portion of the
database owned by a particular user
o CREATE TABLE – defines a table and its columns
o CREATE VIEW – defines a logical table from one or
more views
• Other CREATE statements: CHARACTER SET,
COLLATION, TRANSLATION, ASSERTION,
DOMAIN
9

The following slides create tables forThe following slides create tables for
this enterprise data modelthis enterprise data model
10

12
Non-nullable specifications
Primary key
Some primary keys are composite –
composed of multiple attributes

13
Default value
Domain constraint
Controlling the values in attributes

14
Primary key of
parent table
Identifying foreign keys and establishing relationships
Foreign key of
dependent table

Data Integrity ControlsData Integrity Controls
• Referential integrity – constraint that ensures that
foreign key values of a table must match primary
key values of a related table in 1:M relationships
• Restricting:
o Deletes of primary records
o Updates of primary records
o Inserts of dependent records
15

Using and DefiningUsing and Defining
ViewsViews
• Views provide users controlled access to tables
• Base Table – table containing the raw data
• Dynamic View
o A “virtual table” created dynamically upon request by a user
o No data actually stored; instead data from base table made
available to user
o Based on SQL SELECT statement on base tables or other views
• Materialized View
o Copy or replication of data
o Data actually stored
o Must be refreshed periodically to match the corresponding base
tables
17

Sample CREATE VIEWSample CREATE VIEW
CREATE VIEW EXPENSIVE_STUFF_V AS
SELECT PRODUCT_ID, PRODUCT_NAME, UNIT_PRICE
FROM PRODUCT_T
WHERE UNIT_PRICE >300
WITH CHECK_OPTION;
18
View has a name
View is based on a SELECT statement
CHECK_OPTION works only for updateable views and
prevents updates that would create rows not included in the
view

Advantages of ViewsAdvantages of Views
• Simplify query commands
• Assist with data security (but don't rely on
views for security, there are more important
security measures)
• Enhance programming productivity
• Contain most current base table data
• Use little storage space
• Provide customized view for user
• Establish physical data independence
19

Disadvantages of ViewsDisadvantages of Views
• Use processing time each time view is referenced
• May or may not be directly updateable
20

Create Four ViewsCreate Four Views
CREATE VIEW CUSTOMER_V AS SELECT * FROM CUSTOMER_T;
CREATE VIEW ORDER_V AS SELECT * FROM ORDER_T;
CREATE VIEW ORDER_LINE_V AS SELECT * FROM ORDER_LINE_T;
CREATE VIEW PRODUCT_V AS SELECT * FROM PRODUCT_T;
‘*’ is the wildcard
21

Changing and RemovingChanging and Removing
TablesTables
• ALTER TABLE statement allows you to change
column specifications:
o ALTER TABLE CUSTOMER_T ADD (TYPE VARCHAR(2))
• DROP TABLE statement allows you to remove tables
from your schema:
o DROP TABLE CUSTOMER_T
22

Schema DefinitionSchema Definition• Control processing/storage efficiency:
o Choice of indexes
o File organizations for base tables
o File organizations for indexes
o Data clustering
o Statistics maintenance
• Creating indexes
o Speed up random/sequential access to base table data
o Example
• CREATE INDEX NAME_IDX ON
CUSTOMER_T(CUSTOMER_NAME)
• This makes an index for the CUSTOMER_NAME field of the
CUSTOMER_T table
23

Insert StatementInsert Statement
• Adds data to a table
• Inserting a record with all fields
o INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary Casuals’,
1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601);
• Inserting a record with specified fields
o INSERT INTO PRODUCT_T (PRODUCT_ID, PRODUCT_DESCRIPTION,
PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES
(1, ‘End Table’, ‘Cherry’, 175, 8);
• Inserting records from another table
o INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T WHERE
STATE = ‘CA’;
24

Delete StatementDelete Statement
• Removes rows from a table
• Delete certain rows
o DELETE FROM CUSTOMER_T WHERE STATE = ‘HI’;
• Delete all rows
o DELETE FROM CUSTOMER_T;
29

Update StatementUpdate Statement
• Modifies data in existing rows
UPDATE PRODUCT_T SET UNIT_PRICE = 775
WHERE PRODUCT_ID = 7;
30

SELECT StatementSELECT Statement
• Used for queries on single or multiple tables
• Clauses of the SELECT statement:
o SELECT
• List the columns (and expressions) that should be returned from the query
o FROM
• Indicate the table(s) or view(s) from which data will be obtained
o WHERE
• Indicate the conditions under which a row will be included in the result
o GROUP BY
• Indicate columns to group the results
o HAVING
• Indicate the conditions under which a group will be included
o ORDER BY
• Sorts the result according to specified columns
31

32
Figure 7-8: SQL statement
processing order

SELECT ExampleSELECT Example
• Find products with standard price less than $275
SELECT PRODUCT_NAME, STANDARD_PRICE
FROM PRODUCT_V
WHERE STANDARD_PRICE < 275;
33
Product table

SELECT Example usingSELECT Example using
AliasAlias
• Alias is an alternative column or table name
SELECT CUST.CUSTOMER AS NAME,
CUST.CUSTOMER_ADDRESS
FROM CUSTOMER_V CUST
WHERE NAME = ‘Home Furnishings’;
35

SELECT ExampleSELECT Example
Using a FunctionUsing a Function
• Using the COUNT aggregate function to find totals
• Aggregate functions: SUM(), MIN(), MAX(), AVG(),
COUNT()
SELECT COUNT(*) FROM ORDER_LINE_V
WHERE ORDER_ID = 1004;
36
Order line table

SELECT Example – Boolean OperatorsSELECT Example – Boolean Operators
• AND, OR, and NOT Operators for customizing conditions in WHERE
clause
SELECT PRODUCT_DESCRIPTION, PRODUCT_FINISH,
STANDARD_PRICE
FROM PRODUCT_V
WHERE (PRODUCT_DESCRIPTION LIKE ‘%Desk’
OR PRODUCT_DESCRIPTION LIKE ‘%Table’)
AND UNIT_PRICE > 300;
37
Note: the LIKE operator allows you to compare strings using wildcards. For
example, the % wildcard in ‘%Desk’ indicates that all strings that have any
number of characters preceding the word “Desk” will be allowed

SELECT Example –SELECT Example –
Sorting Results with the ORDER BY ClauseSorting Results with the ORDER BY Clause
• Sort the results first by STATE, and within a state by
CUSTOMER_NAME
SELECT CUSTOMER_NAME, CITY, STATE
FROM CUSTOMER_V
WHERE STATE IN (‘FL’, ‘TX’, ‘CA’, ‘HI’)
ORDER BY STATE, CUSTOMER_NAME;
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Note: the IN operator in this example allows you to include rows whose
STATE value is either FL, TX, CA, or HI. It is more efficient than separate
OR conditions

Categorizing Results Using the GROUP BY ClauseCategorizing Results Using the GROUP BY Clause
SELECT STATE, COUNT(STATE)
FROM CUSTOMER_V
GROUP BY STATE;
Note: you can use single-value fields with aggregate functions if they
are included in the GROUP BY clause
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Customer table

Qualifying Results by CategoriesQualifying Results by Categories
Using the HAVING ClauseUsing the HAVING Clause
• For use with GROUP BY
SELECT STATE, COUNT(STATE)
FROM CUSTOMER_V
GROUP BY STATE
HAVING COUNT(STATE) > 1;
Like a WHERE clause, but it operates on groups
(categories), not on individual rows. Here, only those
groups with total numbers greater than 1 will be
included in final result
40

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SQL Inteoduction to SQL manipulating of data