1. Oracle DML Dr. Bernard Chen Ph.D. University of Central Arkansas

2. SQL code execution To start: SQL> CONNECT system (and then type in password) Then create a file: SQL> edit test(test is file name) remember to store the file in *.sql C:\oraclexe\app\oracle\product\11.2.0\server\bin Once you done coding, execute the code: SQL> @c:\test.sql (test is file name)

3. RETRIEVING DATA FROM A TABLE The main purpose of the SQL language is for querying the database The most important statement or query is the SELECT query The general syntax is SELECT columnlist FROM tablename;

4. RETRIEVING DATA FROM A TABLE Example: SELECT Last, First FROM student;

5. RETRIEVING DATA FROM A TABLE SELECT (*) If you want to see all columns in a table, you do not have to list them all. You can use character asterisk (*) in place of the column list, and all columns will be displayed in the same order as the underlying table structure.

6. RETRIEVING DATA FROM A TABLE RESTRICTING DATA WITH A WHERE CLAUSE A WHERE clause is used with the SELECT query to restrict rows picked The general syntax of the WHERE clause is SELECT columnlist FROM tablename [WHERE condition(s)];

7. RETRIEVING DATA FROM A TABLE SELECT * FROM dept WHERE Location = ‘Monroe’; SELECT Lname, Fname, Salary, Deptid FROM employee WHERE Salary >= 50000;

8. RETRIEVING DATA FROM A TABLE SELECT Lname, Fname, Salary, Dno FROM employee WHERE Salary =25000; SELECT Lname, Fname, Salary, Dno FROM employee WHERE Salary BETWEEN 25000 AND 50000;

9. RETRIEVING DATA FROM A TABLE SORTING The order of rows in a table is arbitrary. You may want to see rows in a specific order based on a column or columns For example, you may want to see employees in alphabetical order by their name

10. RETRIEVING DATA FROM A TABLE The ORDER BY clause is used with the SELECT query to sort rows in a table. The general syntax is SELECT columnlist FROM tablename [WHERE condition(s)] [ORDER BY column|expression [ASC|DESC]];

11. RETRIEVING DATA FROM A TABLE SELECT Last, First FROM student ORDER BY Last; SELECT Last, First FROM student ORDER BY Last DESC;

12. Group Functions The group functions perform an operation on a group of rows and return one result. Sum () Finds sum of all values in a column, ignores null values. Avg () Finds average of all values in a column, ignores null values. Max () Finds maximum value and ignores null values. Min () Finds minimum value and ignores null values. Count(), Count(*) Counts number of rows including nulls for *. Counts non-null values if column or expression is used as argument.

13. Group Functions SELECT SUM(Salary), AVG(Salary), MAX(Salary), MIN(Salary) FROM EMPLOYEE;

14. Grouping Data The rows in a table can be divided into different groups to treat each group separately.

15. Grouping Data The GROUP BY clause is used for grouping data. The general syntax is SELECT column, groupfunction (column) FROM tablename [WHERE condition(s)] [GROUP BY column|expression] [ORDER BY column|expression [ASC|DESC]];

16. Grouping Data SELECT DeptID, COUNT(*) FROM employee GROUP BY DeptID

17. Joins When the required data is in more than one table, related tables are joined using a join condition. In most cases, the common columns are the primary key in one table and a foreign key in another

18. Cartesian Product SELECT Last, First, Name FROM student, faculty;

19. Equijoin The equijoin is a join with a join condition involving common columns from two tables. Join Syntax: SELECT columnnames FROM tablenames WHERE join condition(s);

20. Equijoin SELECT student.Last, faculty.Name FROM student, faculty WHERE student.FacultyID = faculty.FacultyID

21. Table Aliases SELECT s.Last, f.Name FROM student s, faculty f WHERE student.FacultyID = faculty.FacultyID

22. Multiple Joins SELECT e.Lname, d.DeptName, q.QualDesc FROM EMPLOYEE e, Department d, QUALIFICATION q WHERE e.DeptID = d.DeptID AND e.QualID = q.QualID

23. Creating a table using a subquery You can create a table by using a nested SELECT query. The Query will create a new table and populated it with the rows selected from the other table. CREATE TABLE tablename AS SELECT query

24. Creating a table using a subquery CREATE TABLE temp AS SELECT Employee ID, Lname, Fname, Salary FROM employee WHERE DeptID=20; DESCRIBE TABLE SELECT * FROM temp;

25. Set Theory Union Intersect Minus

26. Set theory Syntax Generally, the syntax would looks like: Query Set Operation Query

27. Set theory Syntax Example: Select last from student UNION Select last from faculty

28. UNION Example: To retrieve the social security numbers of all employees who either work in department 5 (RESULT1 below) or directly supervise an employee who works in department 5 (RESULT2 below)

29. UNION DEP5_EMPS   DNO=5 (EMPLOYEE) RESULT1   SSN (DEP5_EMPS) RESULT2   SUPERSSN (DEP5_EMPS) RESULT  RESULT1  RESULT2 The union operation produces the tuples that are in either RESULT1 or RESULT2 or both

30. UNION DEP5_EMPS   DNO=5 (EMPLOYEE) RESULT1   SSN (DEP5_EMPS) RESULT2   SUPERSSN (DEP5_EMPS) RESULT  RESULT1  RESULT2 Select ssn from employee where dno=5 UNION Select superssn from employee where dno=5

31. Intersect Select ssn from employee where dno=5 INTERSECT Select superssn from employee where dno=5

32. Minus Select ssn from employee where dno=5 MINUS Select superssn from employee where dno=5

33. Relational Algebra Overview Relational Algebra consists of several groups of operations Unary Relational Operations SELECT (symbol:  (sigma)) PROJECT (symbol:  (pi)) RENAME (symbol:  (rho)) Relational Algebra Operations From Set Theory UNION (  ), INTERSECTION (  ), DIFFERENCE (or MINUS, – ) CARTESIAN PRODUCT ( x ) Binary Relational Operations JOIN (several variations of JOIN exist) DIVISION Additional Relational Operations OUTER JOINS, OUTER UNION AGGREGATE FUNCTIONS

34. Relational Algebra Overview Relational Algebra consists of several groups of operations Unary Relational Operations SELECT (symbol:  (sigma)) PROJECT (symbol:  (pi)) RENAME (symbol:  (rho)) Relational Algebra Operations From Set Theory UNION (  ), INTERSECTION (  ), DIFFERENCE (or MINUS, – ) CARTESIAN PRODUCT ( x ) Binary Relational Operations JOIN (several variations of JOIN exist) DIVISION Additional Relational Operations OUTER JOINS, OUTER UNION AGGREGATE FUNCTIONS

35. Convert

36. Aggregate Functions and Grouping Use of the Aggregate Functional operation Ʒ Ʒ MAX Salary (EMPLOYEE) retrieves the maximum salary value from the EMPLOYEE relation Ʒ MIN Salary (EMPLOYEE) retrieves the minimum Salary value from the EMPLOYEE relation Ʒ SUM Salary (EMPLOYEE) retrieves the sum of the Salary from the EMPLOYEE relation Ʒ COUNT SSN, AVERAGE Salary (EMPLOYEE) computes the count (number) of employees and their average salary

37. Aggregate Functions and Grouping Grouping can be combined with Aggregate Functions Example: For each department, retrieve the DNO, COUNT SSN, and AVERAGE SALARY A variation of aggregate operation Ʒ allows this: Grouping attribute placed to left of symbol Aggregate functions to right of symbol DNO Ʒ COUNT SSN, AVERAGE Salary (EMPLOYEE)

38. Group Functions

39. Grouping Data The GROUP BY clause is used for grouping data. The general syntax is SELECT column, groupfunction (column) FROM tablename [WHERE condition(s)] [GROUP BY column|expression] [ORDER BY column|expression [ASC|DESC]];

40. JOIN JOIN Operation (denoted by ) The sequence of CARTESIAN PRODECT followed by SELECT is used quite commonly to identify and select related tuples from two relations This operation is very important for any relational database with more than a single relation, because it allows us combine related tuples from various relations

41. JOIN The general form of a join operation on two relations R(A1, A2,..., An) and S(B1, B2,..., Bm) is: R S where R and S can be any relations that result from general relational algebra expressions.

42. Join

43. Set Theory Union Intersect Minus Generally, the syntax would looks like: Query Set Operation Query

44. Natural Join * In oracle, it do have natural join A NATURAL JOIN is a JOIN operation that creates an implicit join clause for you based on the common columns in the two tables being joined. Common columns are columns that have the same name in both tables.JOIN operation

45. Natural join example SELECT * FROM employee NATURAL JOIN department; Type in the code and try to analysis the output.

46. Natural join example SELECT * FROM department NATURAL JOIN Dept_locations; Type in the code and try to analysis the output.

47. Division Unfortunately, there is no division operator in Oracle In order to do division, some complicated processes are required Let us study an example: If we try to find the supplier that supplies all the parts

48. Division Assume we have 2 suppliers and 2 products, the product and supply table looks as following

49. Division We know that supplier #2 supplies all products, and it is our answer to find

50. First of all, find out who did not supply all

51. Then, use all to minus that list

52. Rename “Create Table table_name as” is actually the rename function in Oracle table_name is the rename for table You can also rename the attribute name by adding “new names” after each select item

53. Rename CREATE TABLE analysis AS SELECT dno, AVG(salary) average_salary, MIN(salary) min_salary, MAX(salary) max_salary FROM employee GROUP BY dno;

54. (Not) Exist If a subquery returns any rows at all, EXISTS subquery is TRUE, and NOT EXISTS subquery is FALSE. Syntax: SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2);