On 17 Feb 2014 at 14:10, Simon Slavin <slav...@bigfraud.org> wrote: > On 17 Feb 2014, at 11:37am, Tim Streater <t...@clothears.org.uk> wrote: > >> If I have a text column defined as it might be as MYCOL TEXT (that is with no >> default value), is there a way to distinguish in some row or other between a >> column into which no data has ever been entered, and a column that might have >> been set to a string, but later set to the empty string? (or even only ever >> set to the empty string, perhaps). > > In SQL, "no data" means "NUL" whereas an empty string is a string with zero > characters in. > > So just do > > SELECT typeof(t) FROM myTable > > and see whether you get 'text' or not.
Thanks. I should perhaps have made it clearer that I'm looking at an issue a user has. The application gathers some data from the user via a set of fields they complete in a browser window, which data is then gathered up and sent using ajax to be processed by a PHP script, which writes it to an sqlite db. The user complains that some of this data doesn't make it, so I want to pin down where in the chain this might be failing. Hence my Q. -- Cheers -- Tim
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