As a general rule of thumb, if things are different type, they can't be equal.
One already knows the column type. To compare apples to apples, one
would cast to convert them.
sqlite> SELECT '' = x'';
0
sqlite> SELECT cast('' as blob) = x'';
1
Perhaps some confusion comes from how numbers are stored and compared?
On Thu, Mar 19, 2015 at 11:19 AM, Paul <devgs at ukr.net> wrote:
>> On 3/19/15, Paul wrote:
>> > Maybe this question was already asked and explained.
>> > Or maybe it is documented somewhere (could not fiund it).
>> > Sorry, if this is the case, but why does
>> >
>> > SELECT '' = x'';
>> >
>> > yields 0?
>> >
>>
>> Because it has never before occurred to the developers that somebody
>> would compare a String to a Blob an expect them to be equal to one
>> another.
>
> This may cause very nasty hard-to-find bugs, since SQLite allows to store any
> content inside BLOB field:
>
> sqlite> create table foo(a int, b int, primary key(a, b));
> sqlite> insert into foo(a, b) VALUES(1, ''), (1, x'');
> sqlite> select *, length(b) from foo;
> a b length(b)
> ---------- ---------- ----------
> 1 0
> 1 0
>
> And now, using sqlite3_column_blob() + sqlite3_column_bytes() I 'see' two
> empty blobs, kind of...
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