Chris wrote:
It's not an oddity.
An empty string is a KNOWN value. You know exactly what that value is -
it's an empty string.
A NULL is UNKNOWN - it doesn't have a value at all.
Just to expand on that (and to drag this thread out a little longer), i
find that a pretty good way to get across this difference is to refer to
it as *the* empty string. I prefer this description because it is
implicit that it is still a string. NULL has no type, regardless of the
column it is inserted into. Thus, the empty string is NOT NULL.
brian
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
