How to normalize dates in Normalization [closed] - database

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This is my practice question. I removed the images and added the table into HTML code format.
This below code is of Un Normalized formed.
<table>
<thead>
<tr>
<th>ENo </th>
<th>BNo </th>
<th>Branch </th>
<th>Name </th>
<th>Designation </th>
<th>Salary </th>
<th>DeptNo </th>
<th>DeptName </th>
<th>FromDate </th>
<th>ToDate </th>
</tr>
</thead>
<tbody>
<tr>
<td>1</td>
<td>2</td>
<td>Deer Road</td>
<td>John</td>
<td>Manager</td>
<td>30000</td>
<td>1</td>
<td>HR</td>
<td>05-04-2001</td>
<td>31-12-2006</td>
</tr>
<tr>
<td>1</td>
<td>2</td>
<td>Deer Road</td>
<td>John</td>
<td>Manager</td>
<td>30000</td>
<td>2</td>
<td>Finance</td>
<td>01-01-2007</td>
<td>--</td>
</tr>
<tr>
<td>1</td>
<td>3</td>
<td>Argyll street</td>
<td>Ann</td>
<td>Assistant</td>
<td>8000</td>
<td>1</td>
<td>HR</td>
<td>01-09-2005</td>
<td>--</td>
</tr>
<tr>
<td>2</td>
<td>1</td>
<td>Main Road</td>
<td>David</td>
<td>Supervisor</td>
<td>15000</td>
<td>3</td>
<td>IT</td>
<td>01-07-2002</td>
<td>--</td>
</tr>
</tbody>
</table>
I converted UNF to 1NF by simply adding another Employee ID (EId) column because currently columns are not uniquely identifying.
This below code is of 1NF Form:
.tg {border-collapse:collapse;border-spacing:0;}
.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
overflow:hidden;padding:10px 5px;word-break:normal;}
.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}
.tg .tg-cly1{text-align:left;vertical-align:middle}
.tg .tg-9qwi{background-color:#fd6864;border-color:inherit;font-weight:bold;text-align:center;vertical-align:middle}
.tg .tg-yla0{font-weight:bold;text-align:left;vertical-align:middle}
.tg .tg-vwbk{background-color:#fd6864;text-align:left;vertical-align:bottom}
<table class="tg">
<thead>
<tr>
<th class="tg-9qwi">Eid</th>
<th class="tg-yla0">ENo </th>
<th class="tg-yla0">BNo </th>
<th class="tg-yla0">Branch </th>
<th class="tg-yla0">Name </th>
<th class="tg-yla0">Designation </th>
<th class="tg-yla0">Salary </th>
<th class="tg-yla0">DeptNo </th>
<th class="tg-yla0">DeptName </th>
<th class="tg-yla0">FromDate </th>
<th class="tg-yla0">ToDate </th>
</tr>
</thead>
<tbody>
<tr>
<td class="tg-vwbk">1</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">2</td>
<td class="tg-cly1">Deer Road</td>
<td class="tg-cly1">John</td>
<td class="tg-cly1">Manager</td>
<td class="tg-cly1">30,000</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">HR</td>
<td class="tg-cly1">05-04-2001</td>
<td class="tg-cly1">31-12-2006</td>
</tr>
<tr>
<td class="tg-vwbk">1</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">2</td>
<td class="tg-cly1">Deer Road</td>
<td class="tg-cly1">John</td>
<td class="tg-cly1">Manager</td>
<td class="tg-cly1">30,000</td>
<td class="tg-cly1">2</td>
<td class="tg-cly1">Finance</td>
<td class="tg-cly1">01-01-2007</td>
<td class="tg-cly1">--</td>
</tr>
<tr>
<td class="tg-vwbk">2</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">3</td>
<td class="tg-cly1">Argyll street</td>
<td class="tg-cly1">Ann</td>
<td class="tg-cly1">Assistant</td>
<td class="tg-cly1">8,000</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">HR</td>
<td class="tg-cly1">01-09-2005</td>
<td class="tg-cly1">--</td>
</tr>
<tr>
<td class="tg-vwbk">3</td>
<td class="tg-cly1">2</td>
<td class="tg-cly1">1</td>
<td class="tg-cly1">Main Road</td>
<td class="tg-cly1">David</td>
<td class="tg-cly1">Supervisor</td>
<td class="tg-cly1">15,000</td>
<td class="tg-cly1">3</td>
<td class="tg-cly1">IT</td>
<td class="tg-cly1">01-07-2002</td>
<td class="tg-cly1">--</td>
</tr>
</tbody>
</table>
I converted from 1NF to 2NF by breaking the table into three subtables.
this is 2NF subtables code:
<style type="text/css">
.tg {border-collapse:collapse;border-spacing:0;}
.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
overflow:hidden;padding:10px 5px;word-break:normal;}
.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}
.tg .tg-9ger{background-color:#fcff2f;text-align:left;vertical-align:bottom}
.tg .tg-ctz4{background-color:#3166ff;text-align:left;vertical-align:bottom}
.tg .tg-u24d{background-color:#fcff2f;text-align:left;vertical-align:middle}
.tg .tg-za14{border-color:inherit;text-align:left;vertical-align:bottom}
.tg .tg-7zrl{text-align:left;vertical-align:bottom}
.tg .tg-yla0{font-weight:bold;text-align:left;vertical-align:middle}
.tg .tg-16v0{background-color:#fcff2f;font-weight:bold;text-align:left;vertical-align:bottom}
.tg .tg-exyj{background-color:#34ff34;font-weight:bold;text-align:left;vertical-align:bottom}
.tg .tg-4aos{background-color:#34ff34;text-align:left;vertical-align:bottom}
.tg .tg-xtan{background-color:#3166ff;font-weight:bold;text-align:left;vertical-align:bottom}
.tg .tg-gl5e{background-color:#fcff2f;font-weight:bold;text-align:left;vertical-align:middle}
</style>
<table class="tg">
<thead>
<tr>
<th class="tg-za14"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-yla0">2NF</th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
<th class="tg-7zrl"></th>
</tr>
</thead>
<tbody>
<tr>
<td class="tg-9ger"></td>
<td class="tg-9ger"></td>
<td class="tg-16v0">Employee Table</td>
<td class="tg-9ger"></td>
<td class="tg-u24d"></td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-exyj">Branch Table</td>
<td class="tg-4aos"></td>
<td class="tg-7zrl"></td>
<td class="tg-xtan" colspan="2">Department Table</td>
</tr>
<tr>
<td class="tg-9ger"></td>
<td class="tg-9ger"></td>
<td class="tg-9ger"></td>
<td class="tg-9ger"></td>
<td class="tg-u24d"></td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-4aos"></td>
<td class="tg-4aos"></td>
<td class="tg-7zrl"></td>
<td class="tg-ctz4"></td>
<td class="tg-ctz4"></td>
</tr>
<tr>
<td class="tg-16v0">EId</td>
<td class="tg-16v0">ENo</td>
<td class="tg-16v0">Name</td>
<td class="tg-gl5e">Designation</td>
<td class="tg-gl5e">Salary</td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-exyj">BNo</td>
<td class="tg-exyj">Branch</td>
<td class="tg-7zrl"></td>
<td class="tg-xtan">DeptNo</td>
<td class="tg-xtan">DeptName</td>
</tr>
<tr>
<td class="tg-9ger">1</td>
<td class="tg-9ger">1</td>
<td class="tg-9ger">John</td>
<td class="tg-u24d">Manager</td>
<td class="tg-9ger">30,000</td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-4aos">1</td>
<td class="tg-4aos">Main Road</td>
<td class="tg-7zrl"></td>
<td class="tg-ctz4">1</td>
<td class="tg-ctz4">HR</td>
</tr>
<tr>
<td class="tg-9ger">2</td>
<td class="tg-9ger">1</td>
<td class="tg-9ger">Ann</td>
<td class="tg-9ger">Assistant</td>
<td class="tg-9ger">8,000</td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-4aos">2</td>
<td class="tg-4aos">Deer Road</td>
<td class="tg-7zrl"></td>
<td class="tg-ctz4">2</td>
<td class="tg-ctz4">Finance</td>
</tr>
<tr>
<td class="tg-9ger">3</td>
<td class="tg-9ger">2</td>
<td class="tg-9ger">David</td>
<td class="tg-9ger">Supervisor</td>
<td class="tg-9ger">15,000</td>
<td class="tg-7zrl"></td>
<td class="tg-7zrl"></td>
<td class="tg-4aos">3</td>
<td class="tg-4aos">Argyll Street</td>
<td class="tg-7zrl"></td>
<td class="tg-ctz4">3</td>
<td class="tg-ctz4">IT</td>
</tr>
</tbody>
</table>
after that, I stuck on how to normalized this from the date and to date column.
I need suggestions with which table I have to add this from and to date column?

Answer 1

Normalization never introduces new attributes. You introduced Eid.
This is a practice question, not a real-world database design. For example, employees don't have last names in this design. That's not "real world". But it's a defensible simplification for a practice question.
In the context of a practice question, "Eno" suggests that column should be understood as "Employee number". We'd usually consider "Employee number" in a table like this to be unique, but John and Ann have the same Eno. That raised a red flag for you, and that's a good thing. But in this context, I would have questioned the data first (ask your professor), because that looks like a typo to me. In the context of this practice question, you should consider "Name" to be identifying.
Normalization doesn't proceed by "breaking a table into subtables". Simplifying a little, normalization proceeds by decomposing a table into projections of that table, based on functional dependencies.
You don't have enough information to know what to do with the attributes FromDate and ToDate, because you don't know what those column names mean. That suggests that "FromDate" and "ToDate" are bad names for these columns. Use more descriptive names, so people don't have to guess.
"FromDate" and "ToDate" might have to do with
Designation (John was a manager from FromDate until ToDate),
Branch (John was assigned to Branch from FromDate until Todate),
Department (John was assigned to Department from FromDate until Todate),
Salary (John drew Salary from FromDate until ToDate),
and so on.
This is one place functional dependencies show they're essential.