Relational Database in Access Student System As always please use speaker notes!

Student relational database system We are going to design tables for a system to contain student information. Think of this as the type of information that would be needed for a transcript. We need: Information about the student: idno, name and address, major etc. Information about the courses the students have taken including grade Tables that will allow us to get the name of the major and the name of the course

Student relational database system STUDENT TABLE: Student Idno - this is the primary key since all information relates to it Name Address Phone Social Security # - this is a candidate key since it could be used as a primary key Major code Date enrolled Other information related directly to the student This table has information about the student. All of it must be dependent on the primary key. Clearly we need major information about the major as well, but that cannot be stored on the student table because the name of the major and the chair of the department directly relate to the major code, not to the student idno. Therefore we need a major table. MAJOR TABLE: Major code - this is the primary key Major name Chair department

Student relational database system STUDENT COURSE TABLE: Student Idno Course code Primary key Semester course taken Grade Information about the courses the student has taken can not be kept on the STUDENT TABLE because they are a reoccurring group and thus break the rules of normalization. Essentially if we were to attempt to carry course information on the STUDENT TABLE we would have to determine how many slots we need (the maximum number of courses a student would be allowed to take). This is not practical and it definitely breaks the first normal form rule. The primary key has to be made up of more than one column/field because each student is allowed to take more than one course. The combination of student idno and course code and semester course was taken means that we will have a separate record for each time a course was taken by a student. COURSE TABLE: Course code - Primary key Course name Number credits We cannot keep the course name in the STUDENT COURSE TABLE because the course name directly relates to the course code. This breaks normalization rules. Practically speaking, we would not want to carry the course name in the STUDENT COURSE TABLE because if the course name changes we have to change it on any record. By carrying it on a separate COURSE TABLE, if the name changes we only have one place to enter that change.

Create tables

SELECT student00.studentidno, student00.name, student00.majorcode, major00.majorname FROM student00 INNER JOIN major00 ON student00.majorcode = major00.majorcode; SQL This is the SQL code that Access generated. Notice that each field name has the table name in front of it. The FROM clause does an INNER JOIN which links the student00 table and the major00 table based on the majorcode on student00 being equal to the majorcode on major00. SELECT studentidno, name, student00.majorcode, majorname FROM student00, major00 WHERE student00.majorcode = major00.majorcode; This is alternate SQL code that I wrote. I only used the table name with majorcode because majorcode is the only column in the SELECT that appears in both tables. The FROM clause lists the tables involved in the query. The WHERE clause establishes the link or relationship between the two tables based on the majorcode in student00 and the majorcode in major00.

Relate 3 tables

SELECT stucourse00.studentidno, student00.name, stucourse00.coursecd, course00.coursename, stucourse00.grade FROM (student00 INNER JOIN stucourse00 ON student00.studentidno = stucourse00.studentidno) INNER JOIN course00 ON stucourse00.coursecd = course00.coursecd; SQL

SELECT stucourse00.studentidno, student00.name, stucourse00.coursecd, course00.coursename, stucourse00.grade FROM (student00 INNER JOIN stucourse00 ON student00.studentidno = stucourse00.studentidno) INNER JOIN course00 ON stucourse00.coursecd = course00.coursecd; This is the SQL generated by Access: The SELECT is selecting the columns with the table name in front of each column. In the FROM the relationships are set using the INNER JOIN. This says that student00 and stucourse00 are joined based on the studentidno in each of the tables and then the join is to course00 based on the coursecd in stucourse00 and course00. SQL SELECT stucourse00.studentidno,name, stucourse00.coursecd, coursename, grade FROM stucourse00, student00, course00 WHERE stucourse00.studentidno = student00.studentidno AND stucourse00.coursecd = course00.coursecd; This is alternate SQL code that I wrote: The SELECT is only using table names when column names are not unique. The FROM lists all tables being used in the query. The WHERE shows the relationship between the tables by saying that the studentidno on stucourse00 and student00 must be equal AND the coursecd on stucourse00 and course00 must be equal.

SELECT stucourse00.studentidno, student00.name, student00.majorcode, major00.majorname,stucourse00.coursecd,course00.coursename, stucourse00.grade FROM ((stucourse00 INNER JOIN student00 ON stucourse00.studentidno = student00.studentidno) INNER JOIN course00 ON stucourse00.coursecd = course00.coursecd) INNER JOIN major00 ON student00.majorcode = major00.majorcode; SQL SELECT stucourse00.studentidno, name, student00.majorcode, majorname, stucourse00.coursecd,coursename, grade FROM stucourse00, student00, major00, course00 WHERE stucourse00.studentidno = student00.studentidno AND stucourse00.coursecd = course00.coursecd AND student00.majorcode = major00.majorcode; The SQL that Access generates uses the INNER JOIN to establish the links between the four tables. Note the structure of the INNER JOIN in the example above. The alternate SQL that I coded lists all of the tables in the FROM and then establishes the links through the WHERE.