Getting the next lower value if no result

[Anon]

Hi!
I have a project w/ 2 tables:
table user - contains info about the user and the zip-code the user entered
table zip - contains all the zip codes, longitude,etc.
I know how to get zip codes within a certain range from a certain zip in the zip-table, but now I would like to show zip codes within a certain radius from the user.
The problem is that the table zip is not complete, because some cities have several zip codes and only one of them is stored in the DB.
I would like to query the database and if a zip code doesn't exist I'd like to take the next lower value - but how do I do that (what is the command)?
Any help would be greatly appreciated.🙂
Ciao
Sascha

[Anon]

first check if the zipcode_to_look_for exists. If not, try this:

SELECT max(zip_code)
FROM zip_code_table
WHERE zip_code < zip_code_to_look_for;

This selects the maximum value of zip_code from all zipcodes that are lower than zip_code_to_look_for

You could also combine the two statements, and go for something like

SELECT max(zip_code)
FROM zip_code_table
WHERE zip_code <= zip_code_to_look_for;

This will give either the perfect match, or the next best thing.
But you will have to find a way of telling if the result is the perfect match or the next-best-thing.