将多个参数从单个表传递给函数的优化方法是什么？

Question

我有一个[dbo].[FN_CalcAerialDistance]接受4 parameters并返回其结果的函数。现在 4 个参数来自same table，我不想多次点击数据库来带来相同的数据。我试过了：

SELECT [dbo].[FN_CalcAerialDistance]
    (
       (select latitude from loc.locations where place_name = 'Delhi'),
       (select longitude from loc.locations where place_name = 'Delhi'),
       (select latitude from loc.locations where place_name = 'Mumbai'),
       (select longitude from loc.locations where place_name = 'Mumbai')
    )

有什么方法可以优化代码？我也尝试像数组一样访问表数据类型

Answer 1

作为 Edgars 答案的补充，您无需声明任何变量即可：

SELECT dbo.fn_calcaerialdistance (x.latitude
                                 ,x.longitude
                                 ,y.latitude
                                 ,y.longitude)
FROM loc.locations as x
CROSS JOIN loc.locations y
WHERE x.place_name = 'Delhi'
  AND y.place_name = 'Mumbai' ;

不过，我不希望它表现得更好。

此外，您可以一次计算多个距离

SELECT x.place_name
     , y.place_name
     , dbo.fn_calcaerialdistance (x.latitude
                                 ,x.longitude
                                 ,y.latitude
                                 ,y.longitude)
FROM loc.locations as x
CROSS JOIN loc.locations y
WHERE x.place_name in ('Delhi', 'Bangalore') 
  AND y.place_name = 'Mumbai' ;

Answer 2

这是我唯一能想到的。你可以试试这个作为基础：

DECLARE
    @p1 DECIMAL(12, 9),
    @p2 DECIMAL(12, 9),
    @p3 DECIMAL(12, 9),
    @p4 DECIMAL(12, 9) ;

SELECT @p1 = latitude, @p2 = longitude 
FROM loc.locations 
WHERE place_name = 'Delhi';

SELECT @p3 = latitude, @p4 = longitude 
FROM loc.locations 
WHERE place_name = 'Mumbai';

SELECT dbo.fn_calcaerialdistance (@p1, @p2, @p3, @p4) ;