Practical Database Programming With Java

2.11 Create Oracle 10g XE Sample Database 67

To assign a primary key to our new LogIn table, select the Not Populated from the Primary Key selection list because we don’t want to use any Sequence object to assign any sequence to our primary key. The Sequence object in Oracle is used to automatically create a sequence of numeric number for the primary key. In our case, our primary key is a string, and therefore we cannot use this object. Keep the Primary Key Name, LOGIN_ PK , unchanged, and select the USER_NAME(VARCHAR2) from the Primary Key box. In this way, we select the user_name as the primary key for this table. Since we do not have any Composite Primary Key for this table, just keep this box unchanged. Your finished second step should match one that is shown in Figure 2.45. Click the Next button to continue to the next page—Set the foreign key page.

Since we have not created any other table, therefore, we cannot select our foreign key for this LogIn table right now. We leave this job to be handled later. Click the Next button to go to the next page. The next page allows you to set up some constraints on this table, which is shown in Figure 2.46.

No constraint is needed for this sample database at this moment, so you can click the Finish button to go to the last page to confirm our LogIn table. The opened Confirm page is shown in Figure 2.47.

Click the Create button to create and confirm this new LogIn table. Your created LogIn table should match one that is shown in Figure 2.48 if it is successful. The new created LogIn table is also added into the left pane.

After the LogIn table is created, the necessary editing tools are attached with this table and displayed at the top of this table. The top row of these tools contains object

Figure 2.46. The fourth step—setup constraints.

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Figure 2.47. The last step—confirmation.

Figure 2.48. The created LogIn table.

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Figure 2.49. The opened Data page.

editing tools, and the bottom line includes the actual editing methods.The editing methods include Add Column, Modify Column, Rename Column, and Drop Column, and these methods are straightforward in meaning without question.

To add data into this new LogIn table, you need to use and open the Data object tool in the top row. Click the Data tool to open the Data page, which is shown in Figure 2.49.

Click the Insert Row button to open the data sheet view of the LogIn table, which is shown in Figure 2.50.

Add the following data into the first row:User Name—abrown, PassWord—America, Faculty Id—B66750. Since this user is a faculty, leave the Student Id column blank (don’t place a NULL in here, otherwise you will have trouble when you create a foreign key for this table later!). Your finished first row is shown in Figure 2.50.

Click the Create and Create Another button to create the next row. In the similar way, add each row that is shown in Table 2.23 into each row on the LogIn table.

You can click the Create button after you add the final row into your table. Your finished LogIn table should match one that is shown in Figure 2.51.

Next, let’s create our second table—Faculty table.

2.11.2.2 Create the Faculty Table

Click the Table tool on the top raw and click the Create button to create another new table. Select the Table item to open a new table page. Enter Faculty into the Table Name box as the name for this new table, and enter the following columns into this new table:

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Figure 2.50. The opened data sheet view of the LogIn table.

Table 2.23. The data in the LogIn table

•faculty_id—VARCHAR2(10)

•faculty_name—VARCHAR2 (20)

•office—VARCHAR2 (10)

•phone—CHAR(12)

•college—VARCHAR2 (50)

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Figure 2.51. The completed LogIn table.

•title—VARCHAR2 (30)

•email—VARCHAR2 (30)

The popular data types used in the Oracle database include NUMBER, CHAR, and VARCHAR2. Each data type has its upper bound and low bound.The difference between the CHAR and the VARCHAR2 is that the former is used to store a fixed-length string, and the latter can provide a varying-length string, which means that the real length of the string depends on the number of real letters entered by the user. The data types for all columns are VARCHAR2 with one exception, which is the phone column that has a CHAR type with an upper bound of 12 letters, since our phone number is composed of 10 digits, and we can extend this length to 12 with two dashes. For all other columns, the length varies with the different information, so the VARCHAR2 is selected for those columns.

The finished design view of your Faculty table is shown in Figure 2.52. You need to check the Not Null checkbox for the faculty_id column, since we selected this column as the primary key for this table.

Click the Next button to go to the next page to add the primary key for this table, which is shown in Figure 2.53.

Check the Not Populated from the Primary Key list since we don’t want to use any Sequence object to automatically generate a sequence of numeric number as our primary key, and then select the from the

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textbox. In this way, the faculty_id column is selected as the primary key for this table. Keep the Composite Primary Key box untouched, since we do not have that kind of key in this table, and click the Next button to go to the next page.

Since we have not created all other tables to work as our reference tables for the foreign key, click the Next to continue and we will do the foreign key for this table later. Click the Finish button to go to the Confirm page. Finally, click the Create button to create this new Faculty table. Your completed columns in the Faculty table are shown in Figure 2.54.

Now click the Data object tool to add the data into this new table. Click the Insert Row button to add all rows that are shown in Table 2.24 into this table.

Click the Create and Create Another button when the first row is done, and continue to create all rows with the data shown in Table 2.24. You may click the Create

Figure 2.54. The completed columns in the Faculty table.

Table 2.24. The data in the Faculty table

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Figure 2.55. The finished Faculty table.

button for your last row. Your finished Faculty table should match one that is shown in Figure 2.55.

2.11.2.3 Create Other Tables

In the similar way, you can continue to create the following three tables: Course, Student, and StudentCourse based on the data shown in Tables 2.25–2.27.

The data types used in the Course table are:

•course_id: VARCHAR2(10)—Primary Key

•course: VARCHAR2(40)

•credit: NUMBER(1, 0)—precision = 1, scale = 0 (1-bit integer)

•classroom: CHAR(6)

•schedule: VARCHAR2(40)

•enrollment: NUMBER(2, 0)—precision = 2, scale = 0 (2-bit integer)

•faculty_id VARCHAR2(10)

The data types used in the Student table are:

•student_id: VARCHAR2(10)—Primary Key

•student_name: VARCHAR2(20)

•gpa: NUMBER(3, 2)—precision = 3, scale = 2 (3-bit floating point data with 2-bit after the decimal point)

•credits: NUMBER(3, 0)—precision = 3, scale = 0 (3-bit integer)

•major: VARCHAR2(40)

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Table 2.25. The data in the Course table

Table 2.26. The data in the student table

•schoolYear: VARCHAR2(20)

•email: VARCHAR2(20)

The data types used in the StudentCourse table are:

•s_course_id: NUMBER(4, 0)—precision = 4, scale = 0 (4-bit integer) Primary Key

•student_id: VARCHAR2(10)

•course_id: VARCHAR2(10)

•credit: NUMBER(1, 0)—precision = 1, scale = 0 (1-bit integer)

•major: VARCHAR2(40)