Too much normalization
Recall the definition of the loan
table.
CREATE TABLE loan (
borrower_id INTEGER REFERENCES borrower(id),
bank_id INTEGER REFERENCES bank(id),
approval_date DATE NOT NULL DEFAULT CURRENT_DATE,
gross_approval DECIMAL(9, 2) NOT NULL,
term_in_months SMALLINT NOT NULL,
revolver_status BOOLEAN NOT NULL DEFAULT FALSE,
initial_interest_rate DECIMAL(4, 2) NOT NULL
);
A new design for this table has been suggested to satisfy 1NF. The revised table definition replaces approval_date
with approval_month
, approval_day
, and approval_year
:
CREATE TABLE loan (
...
approval_month SMALLINT,
approval_day SMALLINT,
approval_year SMALLINT,
...
);
This exercise demonstrates how too much normalization can allow for the insertion of invalid data.
This exercise is part of the course
Creating PostgreSQL Databases
Exercise instructions
- Remove the
INSERT INTO
statement that, if executed, would result in invalid data being inserted into the table.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
INSERT INTO loan (
borrower_id, bank_id, approval_month, approval_day,
approval_year, gross_approval, term_in_months,
revolver_status, initial_interest_rate
) VALUES (12, 14, 12, 1, 2013, 421115, 120, false, 4.42);
INSERT INTO loan (
borrower_id, bank_id, approval_month, approval_day,
approval_year, gross_approval, term_in_months,
revolver_status, initial_interest_rate
) VALUES (3, 201, 6, 42, 2017, 30015, 60, true, 3.25);
INSERT INTO loan (
borrower_id, bank_id, approval_month, approval_day,
approval_year, gross_approval, term_in_months,
revolver_status, initial_interest_rate
) VALUES (19, 5, 8, 19, 2018, 200000, 120, false, 6.3);