Generating a Report with PLSQL in Oracle - JOIN USING and JOIN ON

Oracle Database Ideas

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Introduction:

In this scenario we are asked to create a list of all the customers made inactive on a specific date.

This scenario looks like it uses a lot of fields at the top, and it does. There is a lot of information asked for here so we’ll have to do a little “tricky” formatting to get all of the results we want to display. At first, I was going to try to do this with only two tables, but decided to use three instead. No worries, it’s only a tiny bit more involved.

Entity Relationship Diagram

ERD of elements needed for this Oracle Database report.
ERD of elements needed for this Oracle Database report. | Source

Getting Started:

Let’s get started. We’ll look first for the columns we’ll need to display. They want the Customer’s first and last name, their phone number, their email address, the date they were deactivated, the reason they were deactivated, and (here’s the extra) the name of the employee (not just the emp_id) who deactivated the customer. So the first thing we’ll have to do is a bit of formatting. This wasn’t really covered in the class, but I did a little research on my own because I’m just so much of a perfectionist. We need to format the columns that will be displayed at the top of the report so that they will fit within a reasonable span.

COLUMN "Customer Name" FORMAT A18;
COLUMN "Phone" FORMAT A15;
COLUMN "E-Mail" FORMAT A24;
COLUMN "Deactive On" FORMAT A12;
COLUMN "Reason" FORMAT A20;
COLUMN "Employee" FORMAT A10
HEADING 'Employee' JUSTIFY LEFT;

These should be fairly self-explanatory. The command is COLUMN and then you identify the name of the column you want to apply the formatting to (“Customer Name”). Then, using the FORMAT statement we tell Oracle to display the column as a text value (A) of a specified amount of characters wide (18).

Now that that’s over with, let’s get on with the SELECT statement. Some columns will be a concatenation of attributes and some will use special formatting. First, we’ll concatenate the first and last name of the customer using…

SELECT cust_fname || ' ' || cust_lname
"Customer Name",

Then we’ll continue with a crazy formatting of the phone number to give it that “real” phone number look (999)123-4567.

TO_CHAR('(' || SUBSTR(cust_phone, 1,3) ||
')' || SUBSTR(cust_phone, 4,3) || '-' || SUBSTR(cust_phone, 7,10))
"Phone",

We’re still in the SELECT statement here,. So don’t get lost. Now we’re going to continue on with the customer’s email address, date of deactivation, and the name of the employee who deactivated them.

cust_email "E-Mail",
TO_CHAR(deactive_date, 'MM/DD/YYYY') "Deactive On",
reason "Reason",
TO_CHAR(emp_fname) "Employee"

Making The Connection:

Well, that was exhausting! Now it’s time to tell Oracle where to get all this stuff. We’ll use two JOIN statements to connect the three tables that we’re getting data from.

FROM Deactivation d
JOIN Customer c USING (cust_id)
JOIN Employee e ON d.emp_id = e.emp_id

This joins the three tables together through the chan_number attribute between the Customer table and the Deactivation table, and the emp_id between the Deactivation table and the Employee table. That last one is where we get the employee’s first name.

Finally, we need to specify the date that we want to know about. This is the date that the customer became deactivated.

Set The Criteria:

WHERE deactive_date = '30-MAY-2012';

Output:

This is what your output should look like. It doesn’t have to be exact as you are free to “pretty it up” any way you wish, but this shows the basic idea.

Oracle Database report output with JOIN USING and JOIN ON statements.
Oracle Database report output with JOIN USING and JOIN ON statements. | Source

SQL Code for Oracle Report

-- REPORT #4: Inactive customers on a specific date
COLUMN "Customer Name" FORMAT A18;
COLUMN "Phone" FORMAT A15;
COLUMN "E-Mail" FORMAT A24;
COLUMN "Deactive On" FORMAT A12;
COLUMN "Reason" FORMAT A20;
COLUMN "Employee" FORMAT A10 HEADING 'Employee' JUSTIFY LEFT;

SELECT cust_fname || ' ' || cust_lname "Customer Name",
TO_CHAR('(' || SUBSTR(cust_phone, 1,3) || ')' || SUBSTR(cust_phone, 4,3) || '-' || SUBSTR(cust_phone, 7,10)) "Phone",
cust_email "E-Mail", TO_CHAR(deactive_date, 'MM/DD/YYYY') "Deactive On", reason "Reason", TO_CHAR(emp_fname) "Employee"
FROM Deactivation d
JOIN Customer c USING (cust_id)
JOIN Employee e ON d.emp_id = e.emp_id
WHERE deactive_date = '30-MAY-2012';

Conclusion:

Hopefully this tutorial has been useful in helping you to understand the task of creating a simple report using PL/SQL in Oracle. Once you get your SQL statements put together test it on an installation of Oracle to make sure it works.

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