SQL 3. 1

CSE2132 Database Systems

Week 3 Lecture

SQL Data Manipulation

SQL 3. 2

SQL - Structured Query LanguageOriginally designed and implemented by IBM research as the

interface

to a relational database. It is used by Oracle for all interaction with the database.

ANSI Standard SQL-92 defines three levels of compliance, Entry, Intermediate, and Full. Oracle conforms to Entry level compliance, and has many features that conform to Intermediate or Full level compliance. SQL-99 extended SQL-92(Core SQL-99) to a newer object relational form.

A declarative language.

The DBMS performs retrieval. A choice of access routines is made to optimize the query.

SQL specifies syntax features for retrieval update and definition of

the database.

SQL 3. 3

PNAMENUTBOLTCARAVAN

PARTNOP1P2P3

PRICE$0.20$1.00$5000.00

QOH20403

PART

SELECT pname, price*qoh AS pvalue

FROM PART

WHERE price > 0.20 AND price * qoh > 30.0

ORDER BY pname desc;pnameCARAVANBOLT

pvalue$15,000.00$40.00

Example of a Simple SELECT

SQL 3. 4

Further Examples of SELECT

SELECT * FROM PART;

Selects all column values for all rows

SELECT PARTNO, PNAME FROM PART

WHERE PRICE BETWEEN 0.2 AND 1.0;

Selects rows where price ge .2 and le 1.0

SELECT PARTNO, PNAME FROM PART

WHERE PNAME IN ('NUT','BOLT');

Selects rows where pname has a value in the following list

SQL 3. 5

SQL SELECT Statement

SELECT [ALL|DISTINCT]

expression[AS result_column]

{,expression[AS result_column]}

FROM tablename[t_alias]

{,tablename[t_alias]}

[WHERE search_condition]

[GROUP BY colname {,colname}]

[HAVING search_condition]

Nb: This is the syntax of a subselect

SQL 3. 6

The full syntax is then:

subselect

{UNION [ALL] subselect}

[ORDER BY colname[ASC|DESC]

{,colname [ASC|DESC] } ]

Nb: that the search condition in a subselect may be a subselect

SQL SELECT Statement

SQL 3. 7

SQL - Sample DB Schema

PM_NAME BIRTH_YR YRS_SERVED DEATH_AGE STATE_BORN STATE_REP

PRIME _MINISTER

MARRIAGEPM_NAME SPOUSE_NAME MAR_YR PM_AGE NR_CHILDREN

MINISTRY

MIN_NR PM_NAME PARTY DAY_COMM MTH_COMM YR_COMM

SQL 3. 8

Expressions in SELECT

Arithmetic operators are + - ** * /

Comparison operators are = != <> ^= > < >= <=

Logical operators are AND OR NOT

Parentheses may be used to alter order of evaluation - unary, **, * /, + -

Wildcard % = any string of zero or more character

_ = any one character

[ ] = any of the characters enclosed in brackets

A range of numeric, string, date and other functions are available.

SQL 3. 9

Arithmetic Operators in a SELECT

List the name, birth year and year of death of each prime minister who was born in New South Wales. List in order of birth year.

SELECT PM_NAME, BIRTH_YR, BIRTH_YR + DEATH_AGEFROM PRIME_MINISTERWHERE STATE_BORN = ‘NSW’ORDER BY BIRTH_YR

PM_NAME BIRTH_YR BIRTH_YR + DEATH_AGEBarton E 1849 1920Page E C G 1880 1961Chifley J 1885 1951Holt H E 1908 1967McMahon W 1908 ?Whitlam E G 1916 ?

SQL 3. 10

Using the Logical Operators

Which prime ministers were born in Victoria before the turn of the century?

SELECT PM_NAME, BIRTH_YR, STATE_BORNFROM PRIME_MINISTERWHERE STATE_BORN=‘VIC’ AND BIRTH_YR < 1900

PM_NAME BIRTH_YR STATE_BORNDeakin A 1856 VICBruce S M 1883 VICScullin J H 1876 VICMenzies R G 1894 VICCurtin J 1885 VIC

SQL 3. 11

Combining Logical Operators

Which prime ministers were born in NSW and then represented Victoria or have simply not served less than two years?

SELECT PM_NAME, STATE_BORN, STATE_REP, YRS_SERVEDFROM PRIME _MINISTERWHERE STATE_REP = ‘VIC’AND STATE_BORN = ‘NSW’OR NOT YRS_SERVED < 2

PM_NAME STATE_BORN STATE_REP YRS_SERVEDHolt H E NSW VIC 1.88Gorton J G VIC VIC 3.17Whitlam E G NSW NSW 2.92Fraser J M VIC VIC 7.33

SQL 3. 12

Further Examples of SELECT

SELECT PNAME FROM PART

WHERE QOH IS NULL;

Selects those rows where qoh has a null value

SELECT * FROM PART

WHERE PNAME LIKE '_ _T' or PNAME LIKE '%LT';

Selects rows where pname has three letters the last of which is a T or PNAME ends in LT

SQL 3. 13

Use of COUNT with DISTINCT

How many liberal prime ministers were commisioned between 1970 and 1980?

SELECT ‘Liberal PMs’, COUNT(*), COUNT(DISTINCT PM_NAME)FROM MINISTRYWHERE PARTY = ‘Liberal’AND YR_COMM BETWEEN 1970 AND 1980

COUNT(*) COUNT(DISTINCT PM_NAME)

Liberal PMs 5 2

SQL 3. 14

UNION

PNAMENUTBOLTCARAVAN

PARTNOP1P2P3

PRICE$0.20$1.00$5000.00

QOH21403

PART

SELECT pname, 'q1' AS Query FROM PART WHERE QOH < 22

UNION

SELECT pname, 'q2' AS Query FROM PART WHERE QOH > 20;

NUTCARAVANNUTBOLT

q1q1q2q2

pname Query

SQL 3. 15

DELETE FROM tablename [t_alias]

[ WHERE search-condition ]

Delete one or many rows in a table.

In general search-condition and qualification may not involve a sub select on tablename.

DELETE FROM PART WHERE qoh < 4.00;

DELETE

SQL 3. 16

UPDATE

UPDATE tablename [t_alias]

SET colname = expression { , colname = expression}

[ WHERE search_condition ]

Replaces values of the specified columns with expression values for all rows satisfying the search-condition.

Expressions in the set clause may be constants, column values or subqueries.

UPDATE PART

SET price = price * 1.1

WHERE price < 20;

SQL 3. 17

Set Functions in SELECT

PNAMENUTBOLTCARAVAN

PARTNOP1P2P3

PRICE$1.00$1.00$5000.00

QOH20203

PART

Part_count3

Av_price$1667.33

Set functions supported = avg count max min sum

Set functions may not be used directly in a search condition

Price_count2

SELECT count(partno) AS Part_count, avg(price) AS Av_price, count(distinct price) AS Price_count FROM part

SQL 3. 18

Use of GROUP BY

List the number of prime ministers from each party.

SELECT PARTY, COUNT(*)FROM MINISTRYGROUP BY PARTY

PARTY COUNT(*)Country 3Free Trade 1Labor 15Liberal 17National Labor 1Nationalist 3Proctectionist 4United Australia 5

SQL 3. 19

Grouping by More Than One Column

Group prime ministers by their state born and the state they represented. Give the number of prime ministers and the total of years served.

SELECT STATE_BORN, STATE_REP, COUNT(*), SUM(YRS_SERVED)FROM PRIME_MINISTERGROUP BY STATE_BORN, STATE_REP

STATE_BORN STATE_REP COUNT(*) SUM(YRS_SERVED)? NSW 4 9.67? QLD 1 4.81NSW NSW 5 11.83NSW VIC 1 1.88QLD QLD 2 0.13TAS TAS 1 7.25VIC VIC 7 42.69VIC WA 1 3.75

SQL 3. 20

Grouping With the WHERE Clause

For prime ministers born after 1900, list the number of prime ministers born in each state and the total number of years served.

SELECT STATE_BORN, COUNT(*), SUM(YRS_SERVED)FROM PRIME_MINISTERWHERE BIRTH_YR > 1900GROUP BY STATE_BORN

STATE_BORN COUNT(*) SUM(YRS_SERVED)WA 1 ?VIC 2 10.50NSW 3 6.52

SQL 3. 21

Grouping With the HAVING Clause

For each state where the total years served by prime ministers born in that state is less than 10 years, give the number of prime ministers born in that state and the total number of years served.

SELECT STATE_BORN, COUNT(*), SUM(YRS_SERVED)FROM PRIME_MINISTERGROUP BY STATE_BORNHAVING SUM(YRS_SERVED) < 10

STATE_BORN COUNT(*) SUM(YRS_SERVED)TAS 1 7.25QLD 2 0.13

SQL 3. 22

SELECT partno,Count(suppno) AS Supp_count,Sum(qty_supp) AS Total_qty

FROM part_supplier

GROUP BY partno

HAVING count(suppno) > 1PARTNOP1

SUPP_COUNT2

TOTAL_QTY40

PARTNOP1P2P1P3

SUPPNOS1S1S2S2

QTY_SUPP20302010

PART_SUPPLIER

Grouping With the HAVING Clause

SQL 3. 23

Subqueries

Give the name and death age for each prime minister who died at an age less than the average death age of prime ministers.List in ascending order of death age.

SELECT PM_NAME, DEATH_AGEFROM PRIME_MINISTERWHERE DEATH_AGE < (SELECT AVG(DEATH_AGE) FROM PRIME_MINISTER)ORDER BY DEATH AGE

PM_NAME DEATH_AGEHolt H E 59Lyons J A 60Curtin J 60Deakin A 63

SQL 3. 24

Subqueries

Which prime minister died the oldest? Give his name and that age.

SELECT PM_NAME, DEATH_AGEFROM PRIME_MINISTERWHERE DEATH_AGE = (SELECT MAX(DEATH_AGE) FROM PRIME_MINISTER)

PM_NAME DEATH_AGEForde F M 93

SQL 3. 25

Subquery With IN Operator

SELECT DISTINCT DEPUTY_NAME, PARTYFROM DEPUTY_PMWHERE DEPUTY_NAME IN (SELECT PM_NAME FROM PRIME_MINISTER)

DEPUTY_NAME PARTYChifley J B LaborCook J Free Trade Deakin A Protectionist

List the name and party of each deputy prime minister who was also prime minister.

SQL 3. 26

The ANY Operator

PARTNOP1P2P1P3

SUPPNOS1S1S2S2

QTY_SUPP20302510

PART_SUPPLIER

SELECT partno, suppno, qty_supp FROM Part_supplier

WHERE qty_supp > ANY

(SELECT avg(qty_supp) FROM Part-supplier)

PARTNOP2P1

SUPPNOS1S2

QTY_SUPP3025

SQL 3. 27

Multiple Nested Subqueries

Give the name and birth year of each prime minister who wascommisioned after Bob Hawke had turned 21. Order by birth year.

SELECT PM_NAME, BIRTH_YRFROM PRIME_MINISTERWHERE PM_NAME = ANY (SELECT PM_NAME FROM MINISTRY WHERE YR_COMM > (SELECT BIRTH_YR + 21 FROM PRIME_MINISTER WHERE PM_NAME = ‘Hawke R J L’))AND PM_NAME <> ‘Hawke R J L’ORDER BY BIRTH_YR

SQL 3. 28

SubqueriesSELECT partno, suppno, qty_supp FROM Part_supplier

WHERE qty_supp > ANY

(SELECT avg(qty_supp) FROM Part-supplier)

Subqueries may be used in a number of SQL statements.

select, update, insert, delete, create table,

create view, create permit, create integrity

· Subselects may be nested to several levels.

· Special comparison operators are used in additional to =, <>, >, <, etc to indicate comparison to a set of values:

IN equals one of the values returned by the subselect

ANY true if any value returned meets the condition

ALL true if all values returned meet the condition

SQL 3. 29

Correlated Subqueries

PARTNOP1P2P1P2P3

SUPPNOS1S1S2S2S2

QTY_SUPP2030252010

PART_SUPPLIER

SELECT partno, suppno, qty_supp FROM Part_supplier PS1

WHERE qty_supp > ANY

(SELECT avg(qty_supp) FROM Part-supplier PS2

WHERE PS2.partno = PS1.partno)

PARTNOP1P2

SUPPNOS2S1

QTY_SUPP2530

SQL 3. 30

Correlated Subqueries

SELECT partno, suppno, qty_supp FROM Part_supplier PS1

WHERE qty_supp > ANY

(SELECT avg(qty_supp) FROM Part-supplier PS2

WHERE PS2.partno = PS1.partno)

· Subselects (inner queries) are generally executed once and return a set of values to the outer query.

· With a correlated subselect the outer query passes values to the inner query which then evaluates and returns a set of values to the outer query. This process repeats until the outer query terminates.

Which suppliers are supplying more than the average for a part and how much of that part do they supply?

SQL 3. 31

Joining Tables

EMPNOE1E2E3

ENAMEREDBLUEBROWN

MGRNOE1E1E1

DEPTNOD1D1D2

DEPTNOD1D2D3

DNAMETAXPAYLEAVE

EMP DEP

SELECT e.empno AS Number, e.ename AS Name, d.dname AS Department

FROM emp e, dep d

WHERE e.deptno = d.deptnoNumberE1E2E3

NameREDBLUEBROWN

DepartmentTAXTAXPAY

SQL 3. 32

A Search and Join Condition

For each prime minister born in or after 1900, give his name, birth year and party.

SELECT P.PM_NAME, BIRTH_YR, PARTYFROM PRIME_MINISTER P, MINISTRY MWHERE P.PM_NAME = M.PM_NAME AND BIRTH_YR >= 1900

PM_NAME BIRTH_YR PARTYHolt H E 1908 LiberalHolt H E 1908 LiberalMcEwen J 1900 CountryGorton J G 1911 LiberalGorton J G 1911 LiberalGorton J G 1911 Liberal

SQL 3. 33

Multiple Joins

Give the name, birth year, party and the year of marriage of prime ministers born in or after 1900.

SELECT DISTINCT P.PM_NAME, BIRTH_YR, MAR_YR, PARTYFROM PRIME_MINISTER P,PM_MARRIAGE W,MINISTRY MWHERE P.PM_NAME = W.PM_NAMEAND P.PM_NAME = M.PM_NAMEAND BIRTH_YR >= 1900

PM_NAME BIRTH_YR MAR_YR PARTYFraser J M 1930 1956 LiberalGorton J G 1911 1935 LiberalHawke R J L 1929 1956 LaborHolt H E 1908 1946 LiberalMcEwen J 1900 1921 CountryMcEwen J 1900 1968 Country

SQL 3. 34

EMPNOE1E2E3

ENAMEREDBLUEBROWN

MGRNOE1E1E1

DEPTNOD1D1D2

EMP

SELECT X.empno AS Number, X.ename AS Name, Y.ename AS Manager

FROM emp X, emp Y

WHERE X.mgrno = Y.empno

NumberE1E2E3

NameREDBLUEBROWN

ManagerREDREDRED

Joining a Table To Itself

SQL 3. 35

The EXISTS Operator

List the name, birth year and state represented of prime ministers who were also deputy prime ministers.

SELECT PM_NAME, BIRTH_YR, STATE_REPFROM PRIME_MINISTERWHERE EXISTS (SELECT * FROM DEPUTY_PM WHERE DEPUTY_NAME = PM_NAME)

Nb: The subquery always uses “SELECT *” and here the correlationcolumn is PM_NAME. The condition is satisfied if at least one row exists. PM_NAME BIRTH_YR STATE_REP

Deakin A 1856 VICCook J 1860 NSWHughes W M 1862 NSW

SQL 3. 36

The NOT EXISTS Operator

Give the name, state represented and death age of each prime minister who has no recreations.

SELECT PM_NAME, BIRTH_YR, DEATH_AGEFROM PRIME_MINISTER PWHERE NOT EXISTS (SELECT * FROM PM_RECREATION WHERE PM_NAME = P.PM_NAME)

Nb: The subquery returns rows from PM_RECREATION and here thecorrelation column is PM_NAME. The condition is satisfied if no row exists. PM_NAME STATE_REP DEATH_AGE

Reid G H NSW 73Fisher A QLD 66Cook J NSW 87

SQL 3. 37

- Virtual tables because they look and behave like a base table - but contain no data

Views act as a window through which you can see data that is stored in one or many base tables Consider a base table EMP EMPNO ENAME JOB DEPTNO7369 SMITH MANAGER 207568 JONESANALYST 207788 SCOTT CLERK 207469 ALLEN ANALYST 307521 WARD SALESMAN 30

Views or Virtual Tables

SQL 3. 38

CREATE VIEW EMP20 AS SELECT EMPNO,ENAME,JOB FROM EMP WHERE DEPTNO = 20;VIEW EMP20 EMPNO ENAME JOB7369 SMITH MANAGER7568 JONESANALYST7788 SCOTT CLERK

EMP20 data is stored in the EMP base tableColumns used in views inherit the data type and domain of the base table attributes

An SQL View Statement

SQL 3. 39

Emp (empno,empname, salary_pa, deptno)

Dept (deptno, dname)

CREATE VIEW empdetails (empno, empname, dname, salary_fn) AS

SELECT e.empno, e.empname, d.dname,

e.salary / 26

FROM emp e, dept d

WHERE e.deptno = d.deptno;

A View Involving Two Tables

SQL 3. 40

. Updates via views will be reflected in base tables unless the WITH CHECK OPTION is used when the view is created which prevent inserts and updates from creating rows that the view itself cannot select.UPDATE EMP20SET DEPTNO = 30WHERE EMPNO = 7369- the above query would not be allowed if the WITH CHECK OPTION is used as it would remove the row from the view.

. Views can be used to provide security and to simplify queries.View EMP20 - a user who only has access to this view is not able to look at Employees from other Departments.

The WITH CHECK OPTION

SQL 3. 41

You cannot update a view if the view's defining query contains one of the following constructs:

join

set operator

GROUP BY clause

group function

DISTINCT operator

Restrictions on Updating via Views

SQL 3. 42

. Views do not contain any data of their own or occupy storage space

. Views theoretically can be handled the same as base tables

. View definitions are stored in the Catalog

. A view can be defined on top of another view

. Views are created and dropped using SQL Data Definition statements

. Views can be created using any valid SELECT statement

Notes Concerning Views

SQL 3. 43

Example of NOT EXISTSFrom page 161 of Database Systems by C.J.Date 5th edition

Get Supplier names for suppliers who supply all parts.

SELECT SNAME FROM S

WHERE NOT EXISTS

(SELECT * FROM P

WHERE NOT EXISTS

( SELECT * FROM SP

WHERE S# = S.S# AND P# = P.P# ) );

The query may be paraphrased: “ Select supplier names for suppliers such that there does not exist a part that they do not supply.” Note that this query could not be expressed using the negated form of IN. ( Exercise Why not?)