"Brian" <bengelha (AT) comcast (DOT) net> writes:
No, it's not a bug: it's a self-join. If we identified the target table
with the "h" table then it would be impossible to do self-joins in
UPDATE.

You need to write

update
dw.prints_by_hour
set
count = dw.prints_by_hour.count + w.count
from
dw.prints_by_hour_work w
WHERE
w.year = dw.prints_by_hour.year
and w.month = dw.prints_by_hour.month
and w.day = dw.prints_by_hour.day
and w.hour = dw.prints_by_hour.hour

There's been some talk of allowing an alias to be attached to the target
table ("update dw.prints_by_hour h") which would make it possible to
write the update a bit more compactly, but we haven't done that.

regards, tom lane

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