将mysql查询转换为SQL Server

Question

我有一个来自mysql的sql查询，它将以十进制保存的值转换为点（。）。如何将其转换为支持SQL Server？它是SUM（IF - Query。

SELECT routines.date, routines.time, 
SUM( IF( measurements.title =  'T_Temperatur', CAST( REPLACE( routines.value,  ',',  '.' ) AS DECIMAL( 18, 2 ) ), null ) ) AS Temperatur
FROM routines
INNER JOIN measure_routine ON routines.id = measure_routine.routine_id
INNER JOIN measurements ON measure_routine.measure_id = measurements.id
INNER JOIN pools ON measure_routine.pool_id = pools.id
GROUP BY routines.date, routines.time
ORDER BY routines.date, routines.time;

Mysql结果：

这是SQL服务器错误：

Msg 156, Level 15, State 1, Line 2
Incorrect syntax near the keyword 'IF'.
Msg 102, Level 15, State 1, Line 2
Incorrect syntax near ','.

Answer 1

使用SQL标准CASE表达式：

SELECT routines.date, routines.time, 
SUM( CASE WHEN measurements.title =  'T_Temperatur' THEN CAST( REPLACE( routines.value,  ',',  '.' ) AS DECIMAL( 18, 2 ) ) ELSE NULL END) AS Temperatur
FROM routines
INNER JOIN measure_routine ON routines.id = measure_routine.routine_id
INNER JOIN measurements ON measure_routine.measure_id = measurements.id
INNER JOIN pools ON measure_routine.pool_id = pools.id
GROUP BY routines.date, routines.time
ORDER BY routines.date, routines.time;