1. Translation of ER-diagram into Relational Schema Prof. Sin-Min Lee Department of Computer Science CS 157A Lecture 7

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38. An Example CREATE TABLE Student ( ID NUMBER, Fname VARCHAR2(20), Lname VARCHAR2(20), );

40. Not Null Constraint CREATE TABLE Student ( ID NUMBER, Fname VARCHAR2(20) NOT NULL , Lname VARCHAR2(20) NOT NULL , );

41. Primary Key Constraint Primary Key implies: * NOT NULL * UNIQUE. There can only be one primary key. CREATE TABLE Student ( ID NUMBER PRIMARY KEY , Fname VARCHAR2(20) NOT NULL, Lname VARCHAR2(20) NOT NULL, );

42. Primary Key Constraint (Syntax 2)‏ CREATE TABLE Students ( ID NUMBER, Fname VARCHAR2(20) NOT NULL, Lname VARCHAR2(20) NOT NULL, PRIMARY KEY(ID)‏ ); Needed when the primary key is made up of two or more fields

43. Another Table CREATE TABLE Studies( Course NUMBER, Student NUMBER ); What additional constraint do we want on Student? What should be the primary key?

44. Foreign Key Constraint NOTE: ID must be unique (or primary key) in Student CREATE TABLE Studies( Course NUMBER, Student NUMBER, FOREIGN KEY (Student) REFERENCES Students(ID)‏ );

45. Translating ER-Diagrams to Table Definitions

51. Translating Recursive Relationships (without constraints)‏ Employee id name address Manages manager worker Relation: Actor ( worker-id , manager-id )‏ What would be the table definition?