1. null是不可比较的(跟java中的NaN类似),因此其比较操作总是false比如:
update table set channel = #channel# where order_id = 12345 and channel <> ‘AA‘ (如果channel为null,则channel<>‘AA‘也总是不成立的)
2. count distinct的bug:select count(distinct three_part_extend) from table_order where three_part_extend is not null and three_part_extend<>‘{}‘
具体见:http://dinglin.iteye.com/blog/1976026 http://dinglin.iteye.com/blog/1982176
时间: 2024-10-22 12:01:25