1.8.2.2 UPDATE Differences
If you access a column from the table to be updated in an expression, UPDATE
uses the current value of the column. The second assignment in the following statement sets col2
to the current (updated) col1
value, not the original col1
value. The result is that col1
and col2
have the same value. This behavior differs from standard SQL.
UPDATE t1 SET col1 = col1 + 1, col2 = col1;