BIG CITY TAXI TaxiColD TaxiCoNameTaxiStandID NumTaxiCabs NumTaxiFares BL RD YL A

Question

BIG CITY TAXI TaxiColD TaxiCoNameTaxiStandID NumTaxiCabs NumTaxiFares BL RD YL A1 FR BL A1 HT Date 34 Blue Red Yellow A-One Fred's Blue A-One HomeTown 20 20 20 15 15 20 15 15 15-Sep 17 15-Sep 15-Sep 15-Sep 15-Sep 16-Sep 16-Sep 16-Sep 20 6 29 20 17 .The BIG CITY TAXI table captures data about daily taxi fares in a big city . Each taxi company operating in the city has a unique Taxi Company ID Taxi Company name .Each taxi stand in the city has a unique TaxiStandID and a fixed number of taxi cabs Each cab company is permanently assigned to one and only one taxi stand in the city . Each taxi stand can have multiple cab companies assigned to it . Each day, this table records the number of fares in the city for each taxi company 1. Using the BIG CITY TAXI table, describe an example that illustrates the insertion anomaly. 2. Using the BIG CITY TAXI table, describe an example that illustrates the deletion anomaly 3. Depict the full key functional dependencies in the BIG CITY TAXI table 4. Depict the partial functional dependencies (if any) in the BIG CITY TAXI table 5. Depict the transitive functional dependencies (if any) in the BIG CITY TAXI table

Explanation / Answer

Answer is as follows:

1) Insertion Anomaly in BIG CITY TAXI Table:

Insertion anomaly is a stsge when we want to enter a new data into the database due to the absence of other data.

I found in Big City Taxi Table if we want to enter new Taxi stand Id and no of taxis without the knowledge of no of taxi fares leads to the insertion anomaly.

This result in database inconsistencies due to omission.

2) Deleertion Anomaly in BIG CITY TAXI Table:

Deletion anomaly is the unidented loss of the data due to the deletion of other data.

I found in the Big City Taxi Table if want to delete a Taxi Compny Id suppose BL from the table then the other data like Company name BLUE, No. of Taxis and base fares would cease to exit.

It defins how the combining information that does not really belong to each other can cause problems.

3) full Key Functional Dependencies in BIG CITY TAXI Table

The table has following attributes

Date,TaxiComID,TaxiCoName,TaxiSTandID,NumTaxiCabs,NumTaxiFres

According to instructions there the unique Key are two unique keys TaxiComId and TaxiStandId through which we found that TaxiCoName and NumTaxiCabs respectively like:

TaxiComId -> TaxiCoName

TaxiStandId -> NumTaxiCabs

and from Date and TaxiComId NumTaxiFares from both the database as:

TaxiComId,Date ->NumTaxiFares

From above I found that TaxiStandId also be defined by TaxiComId because comapany know on which stand the taxis are. So from all the assumption we get conclusion as follows

TaxiComId -> TaxiCoName,TaxiStandId

TaxiStandId -> TaxiStandName

TaxiComId,Date ->NumTaxiFares

So from Observations we get that

TaxiComId -> TaxiCoName,TaxiStandId,TaxiStandName

TaxiComId,Date ->NumTaxiFares

By Combining both of them we get a key i.e. "TaxiComId,Date" as fully functional dependent key on which all other attributes of the table are dependent.

TaxiComId,Date ->TaxiCoName,TaxiStandId,TaxiStandName,NumTaxiFares

So the Candidate Key or fully functional dependent key of BIG CITY TAXI Table is "TaxiComId,Date".

4) Partial Dependecy

In the above part we cant' found any partial dpendency.

5) Transitive Dependecy

Transitive dependency occur when A->B , B->C so A->C

In the above part we define

TaxiComId -> TaxiCoName,TaxiStandId

TaxiStandId -> TaxiStandName

then

TaxiComId -> TaxiStandName

i.e. clear cut case of transitive dependency.

if there is any query please ask in comments.........

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