When a data as the condition of empty uninitialized (value) :
'=', '!=', '& lt;> 'is invalid, can use' is' is not ' ' 'is null'
Reason: when the duty uninitialized (null) cannot compare,

CodePudding user response:

Well, your progress,

CodePudding user response:

All the basic database is such

CodePudding user response:

You can write blog