Is normalization always necessary and more efficient? - database

Question

I got into databases and normalization. I am still trying to understand normalization and I am confused about its usage. I'll try to explain it with this example.
Every day I collect data which would look like this in a single table:
TABLE: CAR_ALL
ID
DATE
CAR
LOCATION
FUEL
FUEL_USAGE
MILES
BATTERY
123
01.01.2021
Toyota
New York
40.3
3.6
79321
78
520
01.01.2021
BMW
Frankfurt
34.2
4.3
123232
30
934
01.01.2021
Mercedes
London
12.7
4.7
4321
89
123
05.01.2021
Toyota
New York
34.5
3.3
79515
77
520
05.01.2021
BMW
Frankfurt
20.1
4.6
123489
29
934
05.01.2021
Mercedes
London
43.7
5.0
4400
89
In this example I get data for thousands of cars every day. ID, CAR and LOCATION never changes. All the other data can have other values daily. If I understood correctly, normalizing would make it look like this:
TABLE: CAR_CONSTANT
ID
CAR
LOCATION
123
Toyota
New York
520
BMW
Frankfurt
934
Mercedes
London
TABLE: CAR_MEASUREMENT
GUID
ID
DATE
FUEL
FUEL_USAGE
MILES
BATTERY
1
123
01.01.2021
40.3
3.6
79321
78
2
520
01.01.2021
34.2
4.3
123232
30
3
934
01.01.2021
12.7
4.7
4321
89
4
123
05.01.2021
34.5
3.3
79515
77
5
520
05.01.2021
20.1
4.6
123489
29
6
934
05.01.2021
43.7
5.0
4400
89
I have two questions:
Does it make sense to create an extra table for DATE?
It is possible that new cars will be included through the collected data.
For every row I insert into CAR_MEASUREMENT, I would have to check whether the ID is already in CAR_CONSTANT. If it doesn't exist, I'd have to insert it.
But that means that I would have to check through CAR_CONSTANT thousands of times every day. Wouldn't it be more efficient if I just insert the whole data as 1 row into CAR_ALL? I wouldn't have to check through CAR_CONSTANT every time.

Answer 1

The benefits of normalization are dependent on your specific use case. I can see both pros and cons to normalizing your schema, but its impossible to say which is better without more knowledge of your use case.
Pros:
With your schema, normalization could reduce the amount of data consumed by your DB since CAR_MEASUREMENT will probably be much larger than CAR_CONSTANT. This scales up if you are able to factor out additional data into CAR_CONSTANT.
Normalization could also improve data consistency if you ever begin tracking additional fixed data about a car, such as license plate number. You could simply update one row in CAR_CONSTANT instead of potentially thousands of rows in CAR_ALL.
A normalized data structure can make it easier to query data for a specific car. using a LEFT JOIN, the DBMS can search through the CAR_MEASUREMENT table based on the integer ID column instead of having to compare two string columns.
Cons:
As you noted, the normalized form requires an additional lookup and possible insert to CAR_CONSTANT for every addition to CAR_MEASUREMENT. Depending on how fast you are collecting this data, those extra queries could be too much overhead.
To answer your questions directly:
I would not create an extra table for just the date. The date is a part of the CAR_MEASUREMENT data and should not be separated. The only exception that I can think of to this is if you will eventually collect measurements that do not contain any car data. In that case, then it would make sense to split CAR_MEASUREMENT into separate MEASUREMENT and CAR_DATA tables with MEASUREMENT containing the date, and CAR_DATA containing just the car-specific data.
See above. If you have a use case to query data for a specific car, then the normalized form can be more efficient. If not, then the additional INSERT overhead may not be worth it.