사용 CASE/IF :
CASE case_value
WHEN when_value THEN statement_list
[WHEN when_value THEN statement_list] ...
[ELSE statement_list]
END CASE
예, 대신 :
where
`vehicle_tripdetails`.`Param_ID` = '131'
and trip_id = 127) as t1,
(SELECT
time_stamp, `vehicle_tripdetails`.`Param_Data` as speed
FROM
`vehicle_tripdetails`
where
`vehicle_tripdetails`.`Param_ID` = '13'
and trip_id = 127) as t2,
당신은 사용할 수 있습니다
where
`vehicle_tripdetails`.`Param_ID` = '131'
and trip_id = 127) as t1,
CASE
WHEN (SELECT time_stamp, `vehicle_tripdetails`.`Param_Data` as speed FROM
`vehicle_tripdetails` where
`vehicle_tripdetails`.`Param_ID` = '13'
and trip_id = 127)
IS NOT NULL
THEN (SELECT time_stamp, `vehicle_tripdetails`.`Param_Data` as speed FROM
`vehicle_tripdetails` where
`vehicle_tripdetails`.`Param_ID` = '13'
and trip_id = 127)
ELSE
'default value'
END CASE
AS t2
을 사용하여 모든 레코드를 선택하지 않으면 작동합니다. COALESCE()를 참조하십시오. – Strawberry
[MySql Query가 빈 문자열로 NULL을 바꾸기]가 중복 될 수 있습니다. (http://stackoverflow.com/questions/9560723/mysql-query-replace-null-withempty-string-in-select) – Jenn