For MySQL= No data equal to null can be found. Solution

for example , A field has null、“0”、“1” Three , Because the default value is null, Sometimes you need to query null perhaps 0 The data of . If you use it directly xxx ！= “1”, Only query “0” Of . All need to be written in other ways .

1.xxx IS NULL OR xxx != "1"

2.NOT(xxx <=> "1")

because = Can't compare null,<=> Sure .（<> amount to ！=, Can't afford to <=> This kind of inclusion null Comparative effect ）