Need a query

[jamal_dakak]

Hi,
Can someone help me how to formulate a query to find a list of properties within X miles of an entered postcode. It's something related to the coordonates north and east.
Sorry if the question is not clear enough

Thanks 😕

[kakki]

so you need:
a table with a minimum of the following cols:
- postcode
- x-coordinate
- y-coordinate
a table with the following cols:
- place
- x-coordinate
- y-coordiante

after that you can use pythagoras to calculate the distance:
a^2+b2=c2
or ( in your case )
1) select x-coordinate, y-coordinate of postcode
2) select from places where
(postcodeX-placeX)(postcodeX-placeX)+(postcodeY-placeY)*(postcodeY-placeY)<=distance²

the distance is your "within X miles"

[Roger_Ramjet]

More or less true kakki, but not quite.

x and y co-ords will be latitude and longditude in the format degrees:minutes:seconds , not distances in miles.

To do pythagoras you need to convert them to seconds, and then know how many seconds of latitude = 1 mile and how many seconds of longditude = 1 mile at your particular point on the earth's surface: it varies as you move away from the equator.

Since you are talking about very localised distances, the distortion due to the curvature of the earth will not matter.

latitude 42 21' 35" N = ((42360) + (2160) + 35) seconds N
do the same for longditude and then you can begin to do the maths

Subtract latitudes in secs and multiply result by miles per sec at given latitude
Likewise for longditude (miles per sec of latitude is different from miles per sec of longditude, even at the equator)

Now you can use pythagoras

[kakki]

mmmhhhhhhhh.....
i was just thinking on x and y coordinates on "my" map, not a regular map of the earth,
but i have to admit, your solution is more realistic than my "thinking"....

thank you for your comment, i'll try to remember it, next time it comes to coordinates