The type of statement has an effect especially on the UPDATE. If the new value of a column is calculated in an arithmetic expression, an index of this column cannot always be used for the search. Thus the SQL statement
UPDATE <table name>
SET columnx = columnx + 3
WHERE columnx IN (100, 103, 106, 109, 112)
could lead to incorrect results if the index lists with the values 100, 103, 106, 109, 112 were processed little by litte. This must also be taken into consideration when FOR UPDATE is used in the SELECT statement.