My PostgreSQL Portfolio

By: Michael J. Goodlett

CREATE TABLE

Next: Inserting Data

• Now that I have my columns created for the july_finances table, next I just insert the data into the necessary columns using a little creativity.

Inserting The Data

Table Results

• Now I can run SELECT * FROM july_finances to view all the data in the columns and rows of the table I just created.

Here is the remaining data. No need to worry about the values to the right as they are zero.

As you can see I just subtracted the respective SUMs of John’s usd_income minus usd_spent. In addition, I identify this column as

money_left_over by simply adding AS money_left_over in the query.

To compute John’s expected annual salary, given his monthly income remains the same, I ran the above query multiplying the sum of his

July usd_income by 12 and labeled the result as annual_income.

Next: DVD Rental Company

• The following slides will include three new tables (Payment, Staff, & Film) from the database of a DVD rental company.

• I will use SQL queries to return specific types of information using these tables individually and in some scenarios I will incorporate the tables together.

Payment Table Information

Number of Rows – Payment Table

As you can see, the Payment table has exactly 14,596 rows of data.

Staff Table Information

Film Table Information

Number of Rows – Film Table

As you can see, the Film table has a total of 1,000 rows of data.

Joining the Payment & Staff Tables

In this scenario, I joined both tables to return the SUM of the transactions for each employee. This way, I can identify which employee has been the most productive regarding company sales.

Sub-querying: Payment Table

By using the sub-querying method, I was able to return the customer_id (along with the amount) of each customer who spent the MAX amount of money during their respective transactions.

Monthly Sales

By using the EXTRACT function with the timestamp data we have on all transactions, I was able to return the SUM of the amount for monthly sales.

Sub-querying: Film Table

By using the sub-querying method, I was able to return specific information regarding the the titles of the movies which have the MAX rental_rate. I can also identify the years the movies were released along with the ratings and rental amounts.

Conclusion

• The information returned with the SQL queries used in these projects can certainly be used to learn more specific information about the business, reveal the results of a marketing campaign, learn more about the customers & staff, and learn more about the products/services to ensure that better decisions are made based on the historical information we have about the business.