Hello there!
I am a web developer - just started learning though. I am presently creating an information system using SQL database. I have built the application in Visual Studio using Asp.net. I have entered some data in my database and I want some of the options or data to come up automatically in a field when I select a particular option from another field. For example, when I run my program and I select car as an option in the VEHICLE field, the BRAND field should be able to generate automatically from the database and allow the user to choose. If I select MOTORCYCLE as the vehicle then different brands of the motorcycle should be able to automatically generate in the BRAND field. There is already a relationship between the two fields and dependency as well. I was meant to understand that it can be achieved using JavaScript but I don't know how. Please anyone with an idea should help me out.

epospiky:
Hello there!
I am a web developer - just started learning though. I am presently creating an information system using SQL database. I have built the application in Visual Studio using Asp.net. I have entered some data in my database and I want some of the options or data to come up automatically in a field when I select a particular option from another field. For example, when I run my program and I select car as an option in the VEHICLE field, the BRAND field should be able to generate automatically from the database and allow the user to choose. If I select MOTORCYCLE as the vehicle then different brands of the motorcycle should be able to automatically generate in the BRAND field. There is already a relationship between the two fields and dependency as well. I was meant to understand that it can be achieved using JavaScript but I don't know how. Please anyone with an idea should help me out.

Vanilla javascript

change the selected item to see an example<br>
<select name="vehicles" onchange="display_brands(brands = ['camry','bmw','volvo','benz']);"> 
<option value="#" label="default" selected> select</option>
<option value="cars" label="cars">cars</option>
<option value="motocycle" label="motocycle">motocycle</option>
<option value="tricycle" label="tricycle">tricycle</option>
</select>

<select name="brands" id="brands" onchange="what you choose to do here depends on you">
<option value="#" label="default" selected> select</option>
</select>

<br>
your database returns an array of brands from the chosen category and then pass it as an argument to the 
display brands function.
now assume $brands holds the array, you can parse it through JSON 
or whatever you are convenient with 

<script>
function display_brands(input) {

	var brands = input; //<== brands becomes an array object...then;
	document.getElementById('brands').innerHTML = '';
	var i;
	
	//Note: for php this would have been a foreach loop
	for(i=0; i< brands.length; i++)
	{
		var output = document.createElement("option";
		output.value = brands[i];
		output.label = brands[i];
		var t = document.createTextNode(brands[i]);
		output.appendChild(t);
		document.getElementById('brands').appendChild(output);
	}
}
</script>