Just wondering, nowadays…
SQL query? Depends on Server configuration.
With URL strings the situation is a bit different. The allowed length depends on Web Browser and on Web Server + Configuration. It can differ from lets say 1000 characters to a couple of thousands.
Generally, if you need to send larger amount of data to server then it is better to use POST method.
More precise answer here http://www.boutell.com/newfaq/misc/urllength.html , but it might be a bit outdated.