Difference Between Primary Key And Unique Key And Foreign Key And Composite Key

Primary Key

1. Primary Key can identify a row as uniquely 
2. A table can have  only one primary key
3. It can't be Null
4. Indexing added automatically to Primary key

Foreign Key

1. A FOREIGN KEY in one table reference to a Primary Key in another table
2. A table can have  one OR more foreign key.
3. It can be Null 
4. Indexing not added automatically to Foreign key

Unique Key

1. Unique Key can identify a row as uniquely.
2. A table can have  one OR more unique key.
3. It can be Null
4. Indexing not added automatically to Unique Key

Composite Key

1. A composite key contains at least one compound key and one more attribute. Composite keys may also include simple keys and non-key attributes.
2. A table can have one OR more composite Key
3. It can also be null.

See Example:

CREATE TABLE IF NOT EXISTS `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL,
  `email` varchar(100) NOT NULL,
  `phone` varchar(100) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `email` (`email`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

CREATE TABLE IF NOT EXISTS `user_profile` (
  `user_id` int(11) NOT NULL,
  `address1` varchar(100) NOT NULL,
  `address2` varchar(100) NOT NULL,
  KEY `user_id` (`user_id`),
FOREIGN KEY (`user_id`) REFERENCES `users` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Primary Key: users.id
Foreign Key: user_profile.user_id
Unique Key:  users.email

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Goole Map - Track your moving Position on google map- html5

This will enable to you get the current position of your location in mobile. First it will tell your current position on the Google map in form of Pushpin. When you start changing your position then pushpin will start moving. It will be follow you. But GPS and internet must be support by your mobile and off-course it should be enabled in your mobile. It will also work in 2G/3G/4G. It will give your more accurate when you are in City area.

How its work:
It will check your current position with use of browser html5 property. Thats why it ask "Are you want to share your current location".To see your position you must give the access of your current position to the browser. After getting your position it simply plot on google map. When you change your position it recheck the position with use of GPS and update the pushpin on google map.

Initializing...

<style>
    body {font-family: Helvetica;font-size:13pt;padding:0px;margin:0px}
    #map_canvas{display:none; height:100%; width:100%; position:relative;z-index:1;}
    #current {padding:5px; background-color:#000; position:unset; left:0px;z-index:2;text-align:center;width:90%;opacity:0.4;color:#FFF;border-radius:0px 0px 5px 5px; font-weight:bold;}
    #btnCont{position:absolute; bottom:0px; left:0px; width:100%; text-align:center;z-index:2;}</style>


<div id="current">
Initializing...</div>
<div id="map_canvas" style="height: 300px; width: 800px;">
</div>
<div id="btnCont" style="display: none;">
<button onclick="startAgain();"> Restart Tracking</button>
    <button onclick="stopTracking();"> Stop Tracking</button>
</div>
<script charset="utf-8" src="//mapduck.com/js/geoPosition.js" type="text/javascript"></script>
<script src="//maps.google.com/maps/api/js?sensor=false" type="text/javascript"></script>


<script>
    var gmap = null;
    var markers = [];
    var opts = {
        enableHighAccuracy: true,
        timeout: 60000,
        maximumAge: 0
    };
            
    function initialiseMap(){
        var myOptions = {
            minZoom : 3,
            zoom: 10,
            mapTypeControl: true,
            mapTypeControlOptions: {style: google.maps.MapTypeControlStyle.DROPDOWN_MENU},
            navigationControl: true,
            navigationControlOptions: {style: google.maps.NavigationControlStyle.SMALL},
            mapTypeId: google.maps.MapTypeId.ROADMAP      
        } 
        gmap = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
    }
      
    function initialise(){
        if(geoPosition.init())
        {
            document.getElementById('current').innerHTML="Receiving...";
            geoPosition.getCurrentPosition(showPosition,handle_errors,opts);
        }
        else
        {
            document.getElementById('current').innerHTML="Functionality not available";
        }
    }
            
    function handle_errors(error){
        var error_str='';
        switch(error.code)
        {
            case error.PERMISSION_DENIED: 
                error_str="User(you) did not share your geolocation";
                break;
 
            case error.POSITION_UNAVAILABLE: 
                error_str="Could not detect current position";
                break;
 
            case error.TIMEOUT: 
                error_str="retrieving position timed out";
                break;
 
            default: 
                error_str="unknown error";
                break;
        }
        document.getElementById('current').innerHTML=error_str;
    }
   
    function showPosition(p){
        if(gmap == null){
            document.getElementById('map_canvas').style.display = 'block';
            initialiseMap();
        }
        var latitude = parseFloat( p.coords.latitude );
        var longitude = parseFloat( p.coords.longitude );
        document.getElementById('current').innerHTML="Lat = " + latitude.toFixed(2) +" and Long = " + longitude.toFixed(2);
        var location = new google.maps.LatLng( latitude , longitude);
        gmap.setCenter(location);

        var marker = new google.maps.Marker({
            position: location,
            map: gmap,
            title:"You are here"
        });
        markers.push(marker);
    
        var infowindow = new google.maps.InfoWindow({
            content: "<strong>This is your current location.</strong>"
        });
    
        google.maps.event.addListener(marker, 'click', function() {
            infowindow.open(gmap,marker);
        });
        document.getElementById('btnCont').style.display = 'block';
    }
   
    function setAllMap(map) {
        for (var i = 0; i &lt; markers.length; i++) {
            markers[i].setMap(map);
        }
    }
    
    function deleteMarkers() {
        setAllMap(null);
        markers = [];
    }
            
    var watchID = navigator.geolocation.watchPosition(trace,handle_errors,opts);
   
    function trace(position){
        geoPosition.getCurrentPosition(position);
        deleteMarkers();
        showPosition(position);
    }
   
    function startAgain(){
        navigator.geolocation.clearWatch(watchID);
        watchID = navigator.geolocation.watchPosition(trace,handle_errors,opts);
    }   
   
    function stopTracking(){
        navigator.geolocation.clearWatch(watchID);
    }
    google.maps.event.addDomListener(window, 'load', initialise);

</script>

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