관계 연산자 & sql. selection select * from r where a=b and d>5

관계 연산자 관계 연산자 &&SQLSQL

SelectionSelection

SELECT *FROM rWHERE A=B AND D>5

ProjectionProjection

SELECT A,CFROM rWHERE ...

Cartesian ProductCartesian Product

Join - equi, natural joinJoin - equi, natural join

SELECT *FROM r, sWHERE r.B=s.B AND r.D=s.D

Join - Theta joinJoin - Theta join

SELECT *FROM r, sWHERE r.B<s.D

UnionUnion

SELECT *FROM rUNIONSELECT *FROM s

ExampleExample

Example Example - projection- projection

Example Example - select & project- select & project

Example Example - join- join

Example Example - select & project- select & project

Example Example - join- join

SQL SQL 질의 예제질의 예제

관계형 스키마 예제관계형 스키마 예제 EmployeeEmployee (fname, minit, lname, (fname, minit, lname, ssnssn, bdate, address, sex, sala, bdate, address, sex, sala

ry, superssn, dno) ry, superssn, dno)

DepartmentDepartment (dname, (dname, dnumberdnumber, mgrssn, mgrstartdate) , mgrssn, mgrstartdate)

dept_locationsdept_locations ( (dnumberdnumber, , dlocationdlocation) )

ProjectProject (pname, (pname, pnumberpnumber, plocation, dnum), plocation, dnum)

works_onworks_on ( (essnessn, , pnopno, hours), hours)

DependentDependent ( (essnessn, , dependent_namedependent_name, sex, bdate, relationship), sex, bdate, relationship)

질의질의 1 1 - - 기본기본

Retrieve the birthdate and address of the eRetrieve the birthdate and address of the employee whose name is ‘John B.Smith’mployee whose name is ‘John B.Smith’

SELECT bdate, addressSELECT bdate, addressFROM employeeFROM employeeWHERE fname = ‘John’ AND minit=‘B’ AND lname=WHERE fname = ‘John’ AND minit=‘B’ AND lname=

‘Smith’‘Smith’

질의질의 2 2 - - 기본기본

Retrive the name and address of all emploRetrive the name and address of all employees who work for the ‘Research’ departmeyees who work for the ‘Research’ departmentnt

SELECT fname, lname, addressSELECT fname, lname, addressFROM employee, departmentFROM employee, departmentWHERE dname=‘Research’ AND dnumber=dnoWHERE dname=‘Research’ AND dnumber=dno

질의 질의 3 3 - - 기본기본 For every project located in ‘Stafford’ list the pFor every project located in ‘Stafford’ list the p

roject number, the controlling department numroject number, the controlling department number, and the department manager’s last namber, and the department manager’s last name, address, and birthdatee, address, and birthdate

SELECT pnumber, dnum, lname, address, bdateSELECT pnumber, dnum, lname, address, bdateFROM project, department, employeeFROM project, department, employeeWHERE dnum-dnumber AND mgrssn=ssn AND plocation=‘StafWHERE dnum-dnumber AND mgrssn=ssn AND plocation=‘Staf

fod’fod’

질의 질의 4 4 - alisas- alisas 의 사용의 사용

For each employee, retrieve the employee’s first For each employee, retrieve the employee’s first and last name and the first and last name of his and last name and the first and last name of his or her immediate supervisoror her immediate supervisor

SELECT e.fname, e.lname, s.fname, s.lnameSELECT e.fname, e.lname, s.fname, s.lnameFROM employee e sFROM employee e sWHERE e.superssn=s.ssnWHERE e.superssn=s.ssn

질의 질의 5 5 - Tables as Sets- Tables as Sets Make a list of all project numbers for projects that involve aMake a list of all project numbers for projects that involve a

n employee whose last name is ‘Smith’ as a worker or as a n employee whose last name is ‘Smith’ as a worker or as a manager of the department that controls the projectmanager of the department that controls the project

(SELECT pnumber(SELECT pnumberFROM project, department, employeeFROM project, department, employeeWHERE dnum=dnumber AND mgrssn=ssn AND lname=‘SmitWHERE dnum=dnumber AND mgrssn=ssn AND lname=‘Smit

h’)h’)UNIONUNION(SELECT pnumber(SELECT pnumberFROM project, works_on, employeeFROM project, works_on, employeeWHERE pnumber=pno AND essn=ssn AND lname=‘Smith’)WHERE pnumber=pno AND essn=ssn AND lname=‘Smith’)

질의 질의 6 6 - nested query- nested query

Retrieve the name of each employee who has Retrieve the name of each employee who has a dependent with the same first name and saa dependent with the same first name and same sex as the employeeme sex as the employee

SELECT e.fname, e.lnameSELECT e.fname, e.lnameFROM employee eFROM employee eWHERE e.ssn IN (SELECT essnWHERE e.ssn IN (SELECT essn

FROM dependentFROM dependent WHERE essn=e.ssn ANDWHERE essn=e.ssn AND

e.fname=dependent_name ANDe.fname=dependent_name AND sex=e.sex)sex=e.sex)

질의 질의 7 7 - EXIST function- EXIST function

Retrieve the names of employees who havRetrieve the names of employees who have no dependentse no dependents

SELECT fname, lnameSELECT fname, lnameFROM employeeFROM employeeWHERE NOT EXISTS (SELECT *WHERE NOT EXISTS (SELECT *

FROM dependentFROM dependent WHERE ssn=essn)WHERE ssn=essn)

질의 질의 8 8 - - 집합 명시집합 명시

Retrieve the social security number of all eRetrieve the social security number of all employees who work on project number 1,2, mployees who work on project number 1,2, or 3or 3

SELECT DISTINCT essnSELECT DISTINCT essnFROM works_onFROM works_onWHERE pno IN (1,2,3)WHERE pno IN (1,2,3)

질의 질의 9 9 - NULL- NULL 의 사용의 사용

Retrieve the names of all employees who dRetrieve the names of all employees who do not have supervisorso not have supervisors

SELECT fname, lnameSELECT fname, lnameFROM employeeFROM employeeWHERE superssn IS NULLWHERE superssn IS NULL

질의 질의 10 10 - - 집계함수의 사용집계함수의 사용 (1)(1)

Find the sum of the salaries of all Find the sum of the salaries of all employees, the maximum salary, the employees, the maximum salary, the minimum salary, and the average minimum salary, and the average salarysalary

SELECT SUM(salary), MAX(salary), MIN(salary)SELECT SUM(salary), MAX(salary), MIN(salary)FROM employeeFROM employee

질의 질의 11 11 - - 집계함수의 사용집계함수의 사용 (2)(2)

Retrieve the total number of employees in the Retrieve the total number of employees in the company and the number of employees in the company and the number of employees in the ‘Research’ department‘Research’ department

SELECT COUNT(*) FROM employeeSELECT COUNT(*) FROM employee

SELECT COUNT(*)SELECT COUNT(*) FROM employee, departmentFROM employee, department WHERE dno=dnumber AND dname=‘Research’WHERE dno=dnumber AND dname=‘Research’

질의질의 12 12 - - 집계함수의 사용집계함수의 사용 (3)(3)

For each department, retrieve the departmFor each department, retrieve the department number ,the number of employees in tent number ,the number of employees in the department, and their average salaryhe department, and their average salary

SELECT dno, COUNT(*), AVG(salary)SELECT dno, COUNT(*), AVG(salary)FROM employeeFROM employeeGROUP BY dnoGROUP BY dno

질의질의 13 13 - - 집계함수의 사용집계함수의 사용 (4)(4)

For each project on which more than two employeFor each project on which more than two employees work retrieve the project number, project names work retrieve the project number, project name, and number of employees who work on that pre, and number of employees who work on that projectoject

SELECT pnumber, pname, COUNT(*)SELECT pnumber, pname, COUNT(*)FROM project, works_onFROM project, works_onWHERE pnumber=pnoWHERE pnumber=pnoGROUP BY pnumber, pnameGROUP BY pnumber, pnameHAVING COUNT(*) >2HAVING COUNT(*) >2

질의 질의 14 14 - - 집계함수의 사용집계함수의 사용 (5)(5)

For each project, retrieve the project numbFor each project, retrieve the project number, project name, and number of employeeer, project name, and number of employees from department 5 who work on that projs from department 5 who work on that projectect

SELECT pnumber, pname, COUNT(*)SELECT pnumber, pname, COUNT(*)FROM project, works_on, employeeFROM project, works_on, employeeWHERE pnumber=pno AND ssn=essn AND dno=5WHERE pnumber=pno AND ssn=essn AND dno=5GROUP BY pnumber, pnameGROUP BY pnumber, pname

질의질의 15 15 - - 문자열 검색문자열 검색

Retrieve all employees who were born duriRetrieve all employees who were born during the 1950sng the 1950s

SELECT fname, lnameSELECT fname, lnameFROM employeeFROM employeeWHERE bdate LIKE ‘______5_’WHERE bdate LIKE ‘______5_’

질의질의 16 16 - - 산술 연산산술 연산

Find the salary lists to give all employees Find the salary lists to give all employees who work on the ‘Product X’ project a 10% rwho work on the ‘Product X’ project a 10% raiseaise

SELECT fname, lname, 1,1*salarySELECT fname, lname, 1,1*salaryFROM employee, works_on, projectFROM employee, works_on, projectWHERE ssn=essn AND pno=pnumber AND pname=‘ProductX’WHERE ssn=essn AND pno=pnumber AND pname=‘ProductX’

질의질의 15 15 - - 정렬정렬

List ordered by the employee’s departmenList ordered by the employee’s department and within each department ordered alpt and within each department ordered alphabetically by namehabetically by name

SELECT dname, lname, fname, pnameSELECT dname, lname, fname, pnameFROM department, employee, works_on, projectFROM department, employee, works_on, projectWHERE dnumber=dno AND ssn=essn AND pno=pnumberWHERE dnumber=dno AND ssn=essn AND pno=pnumberORDERED BY dname, lname, fnameORDERED BY dname, lname, fname