sql - 在没有额外查询的情况下更新时检查行是否存在？

Question

echo mysqli_query($con, "UPDATE stuff SET fieldd = 2 WHERE bla = 7");

It returns 1 when 7 exists in bla

But it also returns 1 when 7 in bla don't exists, why???? Is there a way to find out if the update was successfull/if this row exists without checking if this row exists with extra query before?

Answer 1

One method uses variables:

SET @found = 0;
UPDATE stuff
    SET fieldd = if(@found := 1, 2, 2)
    WHERE bla = 7;

SELECT @found;

A more formal way is to use mysql_affected_rows() (see here ). By default, though, this only shows if the row has actually changed.