用CASE表达式替换ifs:

Replace ifs with CASE expressions:

   if (latitudinalDifference == 0)
            {
                if (longitudinalDifference != 0)
                {
                    azimuth = Math.PI / 2d;
                }
            }

替换为:

SELECT CASE WHEN @latitudinalDifference = 0 AND @longitudinalDifference <> 0 THEN ...
 ELSE ... END AS azimuth

使用嵌套选择替换连续ifs:

replace consecutive ifs with nested selects:

if(some condition)
{
  i=1; 
}
else
{
 i=2;
}
if(some other condition)
{
  i++; 
}

替换为

SELECT i + CASE WHEN (some other condition) THEN 1 ELSE 0 END
FROM(
SELECT CASE WHEN (some condition) THEN 1 ELSE 2 END AS i
) AS t