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Structured Query Language

Structured Query Language. Querying a Single Table Querying Multiple Tables EXISTS and NOT EXISTS Changing Data. Querying a Single Table. Projections Using SQL SELECT Major FROM STUDENT and SELECT DISTINCT Major FROM STUDENT. Querying a Single Table (Cont.).

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Structured Query Language

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  1. Structured Query Language • Querying a Single Table • Querying Multiple Tables • EXISTS and NOT EXISTS • Changing Data

  2. Querying a Single Table • Projections Using SQL • SELECT Major FROM STUDENT and SELECT DISTINCT Major FROM STUDENT

  3. Querying a Single Table (Cont.) • Selections Using SQL • SELECT Name, Age FROM STUDENT WHERE Major=‘MATH’ AND Age>21 and SELECT Name FROM STUDENT WHERE Major IN [‘MATH’,’HISTORY’]

  4. Querying a Single Table (Cont.) • Sorting • SELECT Name, Major, Age FROM STUDENT WHERE GradeLevel IN [‘FR’,’SO’,’SN’] ORDER BY Major ASC, Age DESC

  5. Querying a Single Table (Cont.) • SQL Built-In Functions • COUNT, SUM, AVG, MAX, MIN • e.g. SELECT COUNT(DISTINCT Major) FROM STUDENT and SELECT Major, COUNT(*) FROM STUDENT WHERE Major IN [‘MATH’,’HISTORY’] GROUP BY Major HAVING COUNT(*)>2

  6. Querying Multiple Tables • Using Subqueries • What are the names of the students enrolled in the class BD445? SELECT Name FROM STUDENT WHERE SID IN (SELECT StudentNumber FROM ENROLMENT WHERE ClassName=‘BD445’)

  7. Querying Multiple Tables (Cont.) • What are the names of the students enrolled in classes on Monday, Wednesday, and Friday at 3 o’clock (MWF3)? SELECT STUDENT.Name FROM STUDENT WHERE STUDENT.SID IN (SELECT ENROLLMENT.StudentNumber FROM ENROLLMENT WHERE ENROLLMENT.ClassName IN

  8. Querying Multiple Tables (Cont.) (SELECT CLASS.Name FROM CLASS WHERE CLASS.Time=‘MWF3’))

  9. Querying Multiple Tables (Cont.) • Joining with SQL • List the student number and class name of all students named RYE who were first to enroll in a class. SELECT STUDENT.SID, ENROLMENT.ClassName FROM STUDENT, ENROLLMENT WHERE STUDENT.SID=ENROLLMENT.StudentNumber AND ENROLLMENT.PositionNumber=1 AND STUDENT.Name= ‘RYE’

  10. Querying Multiple Tables (Cont.) • EXISTS and NOT EXISTS • List the student numbers of students enrolled in more than one class. SELECT DISTINCT StudentNumber FROM ENROLLMENTA WHERE EXISTS (SELECT * FROM ENROLLMENTB WHERE A.StudentNumber=B.StudentNumber AND A.ClassName NOT = B.ClassName)

  11. Querying Multiple Tables (Cont.) • CHANGING DATA • Inserting Data INSERT INTO ENROLLMENT VALUES(400,’BD445’,44) • Deleting Data DELETE STUDENT WHERE STUDENT.Major=‘Accounting’ • Modifying Data UPDATE ENROLLMENT SET PositionNumber=44 WHERE SID=400

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