On 14 Jul 2010, at 5:13pm, Richard Hipp wrote:
> Improvements to the IN operator documentation can be found here:
>
> http://www.sqlite.org/draft/lang_expr.html#in_op
I find that table difficult to understand: you have some mutually exclusive
columns. Could it be replaced by this sequence of four tests and an
'otherwise' ?
If the right op is the empty list, then IN = false
else if the left op is NULL, then IN = NULL
else if the right op contains left op, then IN = true
else if the right op contains NULL, then IN = NULL
otherwise IN = false
Also NOT true = false, NOT false = true, NOT NULL = NULL.
That should match the source code, so it should be better documentation.
By the way, can someone explain why this rule, equivalent to line 4 of the
table, is there:
else if the right op contains NULL, then IN = NULL
By the time we've got there we already know that the left op is not NULL. Why
does the handling of a NULL right op require a special case like that ? We
definitely know that the left op is not IN it.
Simon.
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