Thread: How to search for a part of a number

Hi,

I'm wondering if there was a clever way to find parts of a numeric 
string in another table.
There is a table that holds city-codes and city-names. City-code would 
be the part of a phone number that identifies the city.
Over here this code can have 2 - 5 digits. So the table would contain:
23 ; A-City
345 ; B-Town
4455 ; C-Village
632 ; D-Town
...

I'm quite sure the numbering system is bound to be spanning a search tree.

So there are 2 tasks:
a)   I'd get 445598765 in and like to know the corresponding city
b)   I'd like to get the number nicely formatted :  4 4 55987-65  -->  
4455 / 98765

Obviously one could do it on the client side.
As I dont know how many digits in the input are relevant, I need to try 
the shortest code first.
1)  search for 44
2)  add 5 and search for 445
3)  add the 2nd. 5 and search for 4455
BINGO

Is there a way to do it within the db?

In article <4CC4D3E2.7090302@gmx.net>,
Andreas <maps.on@gmx.net> writes:

> Hi,
> I'm wondering if there was a clever way to find parts of a numeric
> string in another table.
> There is a table that holds city-codes and city-names. City-code would
> be the part of a phone number that identifies the city.
> Over here this code can have 2 - 5 digits. So the table would contain:
> 23 ; A-City
> 345 ; B-Town
> 4455 ; C-Village
> 632 ; D-Town
> ...

> I'm quite sure the numbering system is bound to be spanning a search tree.

> So there are 2 tasks:
> a)   I'd get 445598765 in and like to know the corresponding city

If the prefixes are unique:
 SELECT code, name FROM tbl WHERE '445598765' LIKE code || '%'

If not:
 SELECT code, name FROM tbl WHERE '445598765' LIKE code || '%' ORDER BY length(code) DESC LIMIT 1

If your table is so large that seqscans hurt you, use the 'prefix'
contrib package.