I have always (or at least intended to) treat NULL and empty strings separately in my SQL querying history. Now I have run across something that mystifies me (but probably shouldn't) that I would like an explanation for.
Consider this bit o' code:
DECLARE @ORDER CHAR(10)
SET @ORDER=
(
SELECT NULL
)
IF @ORDER <> ''
PRINT 'Not an empty string'
IF @ORDER IS NULL
PRINT 'It is NULL'
Run this and you will get:
It is NULL
I was expecting:
Not an empty string
It is NULL
Why is NULL not passing the 'not an empty string' test? In other words, how does NULL = '' ? Is NULL cast to an empty string for this comparison?
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Well met,
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PHP Code:
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