One .redis Knowledge about

1.SET key value

meaning ：

          String value value Related to key .

          If key Has held other values , SET Just overwrite the old value , Ignore the type .

example ：

2.SETEX key seconds value

meaning ：

            Will value value Related to key , And will key The lifetime of is set to seconds ( In seconds ).

            If key Already exist , SETEX The command will override the old value .

Return value ：

            When the setting is successful, return OK .

            When seconds When the parameter is illegal , Return an error .

3.SETNX key value

meaning ：

            take key The value of the set value , If and only if key non-existent .

            If a given key Already exist , be SETNX Don’t do anything .

           SETNX yes 『SET if Not eXists』( If it doesn’t exist , be SET) Abbreviation .

Return value ：

            Set up the success , return 1 .

            Setup failed , return 0 .

example ：

4.GETSET key value

meaning ：

          Will be given key The value of the set value , And back to key The old value (old value).

          When key When it exists but is not a string type , Return an error .

Return value ：

            Return to a given key The old value .

            When key When there is no old value , That is to say , key When there is no , return nil .