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CODD’S RULES FOR RDBMSs
Information representation
Guaranteed access
Dynamic on-line catalog
Comprehensive data sub-language
View updating
Note: Codd was a research fellow at IBM in the ’70s
Codd has written a paper in which he outlined the rules forrelational systems. These are as follows:
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High-level insert, update and delete
Physical data independence
Logical data independence
Integrity independence
Distribution independence
Non-subversion
CODD’S RULES FOR RDBMSs..
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CODD’S RULES FOR RDBMSs
Information representation -- all information should be represented as atomic values
in tables.
Guaranteed access -- given a row, column and table name we should be able to
access values in the table.
Online catalog -- the system catalog (data dictionary) should be online
and accessible by the system.
Comp. data lang. -- there should be a language for data definition and data
manipulation.
View updating -- the system must be able to automatically update views
based on a base table.
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CODD’S RULES FOR RDBMSs
High level insertion, update.. -- insertion, deletion and update should operate on a
table.
Physical data independence -- should be able to change internal storage structures
without affecting application programs.
Logical data independence -- should be able to change logical scheama
without affecting application programs.
Integrity independence -- integrity controls must be independent of appln. prog.
Distribution independence -- the users/appln. programs should not be affected
by where the data is physically stored.
Non subversion -- should not be able to bypass integrity rules by
using the data sub language.
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based on relational calculus (uses select, project, join etc.)
standardized in ’82,’95, ‘05 Embedded SQL a standard in ‘89 Two major types and three other types
DDL, DMLSQL/T, SQL/I, DCLEmbedded SQL
STRUCTURED QUERY LANGUAGEStructured Query Language originated from SEQEL (early 1980’s). SQL (is/was):
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There are five types of SQL as follows:
DDL - Creating / modifying tables, views and indexes
DML - Retrieving / inserting / updating information
SQL/T - Transaction boundaries
SQL/I - Integrity constraints
DCL. - To authorize access to the database objects
STRUCTURED QUERY LANGUAGE
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DATA DEFINITION LANGUAGE
Create/Open Database (not discussed) Create Schema Employee; Create/Alter/Drop Table Create/Drop View Create/Drop Index
DDL is the language used to define/modify the databaseSchema.
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DATA DEFINITION LANGUAGE..
Action DatabaseComponent ComponentName…
TYPICAL FORMAT
Create Drop
TableViewIndex
Cust…..Emp…..…………
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Alter Table Emp…..
CREATE TABLE Table name (attribute attr. type, attribute attr.type..)[CONSTRAINT Constr name TYPE attr];
ALTER TABLE Table name ADD attr. attr. type, attr. attr. type;
DATA DEFINITION LANGUAGE..
Command used to create tables
Command used to change attributes in tables
Command used to delete table definitions
DROP TABLE Table name ;
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CREATE TABLE
Dept.
d_no d_name d_mgr_ssn d_phone
CREATE TABLE DEPT. ( d_no Integer, d_name VarChar(15), d_mgr_SSN Char(9), d_phone Char(12));
Creates a table (schema)
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ALTER, DROP TABLE
Dept.
d_no d_name d_mgr_ssn d_phone no_of_emp
ALTER TABLE DEPT. ADD no_of_emp Integer;
DROP TABLE Dept.;
Alter table adds/drops attributes; Drop table drops the entire table.
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ALTER TABLE DEPT. DROP no_of_emp;
CREATE VIEW Viewname AS SELECT...
CREATE VIEW
Command used to create VIEWS
A view is the way a user looks at the data.
Views are subsets of the data in the database.
A view could include data from more than one table.
All application programs access data via views.
Views provide logical data independence.
Reports can be created from views (as well as from tables)
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CREATE VIEW..
Emp.
e_ssn e_name e_title
CREATE VIEW AnalystsAS SELECT e_name, e_title FROM Emp. WHERE e_title = “analyst”;
Create a view of employees who are analysts
Creates a query; AS is an “alias” or name
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DROP VIEW ANALYSTS;
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CREATE/DROP INDEX
CREATE INDEX TI_INDEXON EMP(e_title);
DROP INDEX TI_INDEX;
An index is an example of file organization used to facilitate retrieval
DATA MANIPULATION LANGUAGE
INSERTinsert a record
UPDATEchange values
DELETEdelete records
SELECTchoose record
DML is the language used to create/modify and deletedata in the database.
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THE INSERT COMMAND..
INSERT INTO TABLENAMEVALUES (attr1 value, attr2 value….);
FORMAT
Inserts a record into a table with name TABLENAME.
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THE INSERT COMMAND..
INSERT INTO EMPVALUES (‘978-98-9878’, ‘Sullivan’, ‘developer’);
Insert employee record
EMP.
e_ssn e_name e_title
e_ssn e_name e_title
978-98-9878 Sullivan developer
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THE UPDATE COMMAND
EMP.
e_ssn e_name e_title
UPDATE EMPSET e_title = ‘analyst’WHERE e_name = ‘Sullivan’;
Update employee title to ‘analyst’
/* table name *//* new values *//* condition */
e_ssn e_name e_title
978-98-9878 Sullivan analyst
EMP.
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THE DELETE COMMAND
DELETE FROM EMP.WHERE e_name = ‘Sullivan’;
Delete Employee record
e_ssn e_name e_title
EMP.
e_ssn e_name e_title
978-98-9878 Sullivan analyst
What if you were to issue,DELETE FROM EMP?
EMP.
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THE SELECT STATEMENT
SELECT <Attribute list>FROM <Relations>[WHERE <Conditions> AND/OR <Conditions>]
[GROUP BY <Attribute list>][HAVING <Conditions>]
[ORDER BY <Attribute list> DESC/ASC];
Group by is used to organize data into groups and provide summary
information. Having is used for the group condition.
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ADDITIONAL NOTES ON SELECT
The Select part can include literals (“The number of..”)
Some functions can be included in SELECT part or WHERE part
More than one table and one condition can be specified
Conditions are connected by logical operators -- and/or etc.
When GROUP BY is used, the WHERE clause is not used.
Instead the group condition is specified by HAVING.
ORDER BY is optional and used if sorting is required.
Notes on the select statement
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FUNCTIONS IN SQL
Logical Arithmetic String Date
IN WHICH PART OF THE QUERY ARE FUNCTIONS USED?
Operators to carry out different types of calculations
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LOGICAL OPERATORS
“=“, “>“, “<“ “>=“, “<=“ “<>“ OR “!=“ (NOT) BETWEEN X1 AND X2 (inclusive) LIKE“_” or “%” IN(NOT) NULL
FinanceFinancial Records
Logical operators are generally used to carry out comparison
(Select….Where D_Name like “%fin%”)
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d_name d_phone
Finance 845-9878
Sales 989-0087
Marketing 787-9934
Fin. records 884-5768
Dept.
LOGICAL OPERATORS..
Select cust.cust#From custWhere cust.zip in (61455, 60601….)
Select emp#, emp nameFrom empWhere income between 70000 and 90000;
To select customers in Macomb, Chicago or Bloomington
To select employees between certain income range
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cust# zip
1156 61455
1157 61455
1158 54555
1160 60601
Cust.
BUILT-IN ARITHMETIC FUNCTIONS
ABS ROUND TRUNC COUNT SUM AVG MAX MIN
Select count(emp_name)… Select max(emp_salary)…..
Arithmetic functions are used to carry out math operations
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STRING FUNCTIONS
LENGTH(string) SUBSTR(string, start, no of ch.) LOWER UPPER
Select substr(prob_descr, 0, 10)………
String functions are used to carry out string manipulation
Prob_descr = “I am unable to log in…”
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DATE FUNCTIONS
ADD_MONTHS(1/1/15, 5) = 6/1/15 MONTHS_BETWEEN (sysdate, hiredate) NEXT_DAY(hiredate, ‘Friday’) TO_DATE(string, picture)
TO_DATE(“12/09/14”, ‘DY th MM, YYYY’) = 9 th DEC, 2014
Next_day(2/20/14, ‘Friday’) = 2/21/14
Date functions are used to carry out date arithmetic
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SIMPLE RETRIEVALS
EMP.
e_ssn e_name e_title
SELECT e_nameFROM EMPWHERE e_title = ‘analyst’;
Select employees who are analysts
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EMPLOYEEEMPLOYEE
SIMPLE RETRIEVALS..
e_ssn e_name e_title e_salary
456-34-8895 Smith developer $35,000
459-66-6785 Johnson analyst $27,000
467-89-8898 Weintraub developer $60,000
478-64-8005 Dickson manager $64,000
489-12-5575 Ferrel analyst $47,000
492-93-4438 Rao analyst $71,000
467-89-8898 McDonald manager $85,000
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SIMPLE RETRIEVALS..
SELECT e_nameFROM EMPWHERE e_name like ‘%son’
Select employees whose name ends with ‘son’
EMP.
e_ssn e_name e_title
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SIMPLE RETRIEVALS..
SELECT e_nameFROM EMPWHERE e_name not like ‘a%’
Select employees whose name does not begin with ‘a’
EMP.
e_ssn e_name e_title
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RETRIEVALS WITH AGGREGATES..
SELECT COUNT(e_name)FROM EMPWHERE e_title = ‘developer’
Count the number of developers
EMP.
e_ssn e_name e_title
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SELECT “Average Salary=“, Avg(e_salary) From EMPWhere e_title = ‘developer’ or e_title = ‘analyst’ ;
EMP.
e_ssn e_name e_title e_salary
RETRIEVALS WITH AGGREGATES..
What does this query do?
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RETRIEVALS WITH EXPRESSIONS..
List employees and their witholdings (calculated as8% of salary).
EMP.
e_ssn e_name e_title e_salary
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SELECT e_name, e_salary * 0.08 AS WithholdingsFROM EMP
RETRIEVALS WITH GROUP BY..
SELECT e_title, COUNT(e_name)FROM EMPGROUP BY e_title
List all job titles and the number of emps in each
EMP.
e_ssn e_name e_title
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GROUP BY..
EMPLOYEEEMPLOYEE
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e_ssn e_name e_title e_salary
456-34-8895 Smith developer $35,000
459-66-6785 Johnson analyst $27,000
467-89-8898 Weintraub developer $60,000
478-64-8005 Dickson manager $64,000
489-12-5575 Ferrel analyst $47,000
492-93-4438 Rao analyst $71,000
467-89-8898 McDonald manager $85,000
RETRIEVALS WITH HAVING..
List the number of employees in each job category with salary > $50,000
SELECT “Number of: “, e_title, “=“, COUNT(e_name)FROM EMPGROUP BY e_title HAVING e_salary > 50000
EMP.
e_ssn e_name e_title e_salary
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RETRIEVALS WITH HAVING..
EMP.EMP.
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e_ssn e_name e_title e_salary
456-34-8895 Smith developer $35,000
459-66-6785 Johnson analyst $27,000
467-89-8898 Weintraub developer $60,000
478-64-8005 Dickson manager $64,000
489-12-5575 Ferrel analyst $47,000
492-93-4438 Rao analyst $71,000
467-89-8898 McDonald manager $85,000
RETRIEVAL FROM MULTIPLE TABLES
Sharing of information a key concept Normalization process leads to multiple tables When data is retrieved from > 1 table, need to
link tables together This is done by equating FK values with PK values
for each set of tables that need to be linked
Emp.
emp#, emp name, dept#
Dept.
dept#, dept name, mgr
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RETRIEVAL FROM MULTIPLE TABLES
Dept.
d_name d_no d_mgr_ssn d_phone
SELECT Emp.e_name, Dept.d_nameFROM EMP, dept.WHERE EMP.e_ssn = dept.d_mgr_ssn
EMP.
e_ssn e_name e_title
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RETRIEVAL FROM MULTIPLE TABLES..
DEPARTMENT
EMPLOYEE
d_name d_no d_mgr_ssn d_phone
Manugistics 142 467-89-8898 845-9878
IMS 230 479-99-0045 989-0087
Pilot 345 478-64-8005 787-9934
InfoSec 467 898-98-0967 884-5768
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e_ssn e_name e_title e_salary
456-34-8895 Smith developer $35,000
459-66-6785 Johnson analyst $27,000
467-89-8898 Weintraub developer $60,000
478-64-8005 Dickson manager $64,000
489-12-5575 Ferrel analyst $47,000
492-93-4438 Rao analyst $71,000
467-89-8898 McDonald manager $85,000
DISCUSSION Write SQL queries for the following:
1. Create Emp table with E_SSN, E_Name, E_title as attr. -- assume data types.
2. Add E_salary to the Employee table.
3. Create an index, “Ti_ndx” on E_title.
4. Insert Bob White with SS# 556455555 as an analyst
5. List employees and job titles in order of title.
6. List employees other than developers.
7. Create a view “hi_flier” listing developers with salary > $100K.
8. Count the #. of employees who are managers.
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