Question

我在我的桌子上这样做:

“entergraph

<代码>id和bolag_id>:int>。

如果我使用<代码>lngized栏,则不退还结果:

<><>t>>t = > 学历: * 源自地点: WHERElngized = 13.8461208

然而,如果我使用<代码>lat栏,则does 返还结果:

lat Query: SELECT * FROM location_forslag WHERElat= 58.3902782

What is the problem with the lngitude column?

Answer 1

It is not generally a good idea to compare floating point numbers with = equals operator.

比较使用=操作员的2个环流点数字是否正确?

处理浮点数字的准确性问题

如果你提出申请,你需要考虑一下,你想要回答的是多么接近。

1度约为112千米,0.00001度约为1.1米(赤道)。如果两点不同,0.00000001度=1毫米,你是否真的要说“不等于”?

set @EPSLION = 0.00001  /* 1.1 metres at equator */

SELECT * FROM location_forslag 
WHERE `lngitude` >= 13.8461208 -@EPSILON 
AND `lngitude` <= 13.8461208 + @EPSILON

This will return points where lngitude is within @epsilon degrees of the desired value. You should choose a value for epsilon which is appropriate to your application.

Answer 2

烟雾点为:。

 WHERE ABS(lngitude - 13.8461208) < 0.00000005

Answer 3

相形浮体为 compare。我有同样的问题,并解决了这一问题:

SELECT
    [dbo].[Story].[Longitude],
    [dbo].[Story].[Latitude],
    [dbo].[Story].[Location],
FROM
    [dbo].[Story],
    [dbo].[Places]
WHERE
    convert(decimal, [dbo].[Story].[Latitude]) = convert(decimal,  [dbo].[Places].[Latitude])
    and
    convert(decimal, [dbo].[Story].[Longitude]) = convert(decimal, [dbo].[Places].[Longitude])
    and
    [dbo].[Places].[Id] = @PlacesID 
    and
    [dbo].[Story].IsDraft = 0
ORDER BY
    [dbo].[Story].[Time] desc

Look at the first 3 rows after the WHERE clausule. Hope it helps.

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