MySQL如何根据WHERE子句中参数的顺序获取结果

Question

I have the following query statement:

SELECT idelm_na AS ID, nd.lat_nd AS lat, nd.lon_nd AS 'lon' , adr.road_adr AS 'road' 
FROM node_nd nd, node_address_na na, address_adr adr
WHERE 
    ((ROUND(lat_nd,6)=ROUND(14.654733,6) AND ROUND(lon_nd,6)=ROUND(121.058403,6)) OR 
    (ROUND(lat_nd,6)=ROUND(14.654791,6) AND ROUND(lon_nd,6)=ROUND(121.062386,6)) OR
    (ROUND(lat_nd,6)=ROUND(14.654791,6) AND ROUND(lon_nd,6)=ROUND(121.064343,6)) OR
    (ROUND(lat_nd,6)=ROUND(14.654754,6) AND ROUND(lon_nd,6)=ROUND(121.064403,6)) OR

    (ROUND(lat_nd,6)=ROUND(14.654648,6) AND ROUND(lon_nd,6)=ROUND(121.06445,6)) OR 
    (ROUND(lat_nd,6)=ROUND(14.653869,6) AND ROUND(lon_nd,6)=ROUND(121.064798,6)) OR
    (ROUND(lat_nd,6)=ROUND(14.653865,6) AND ROUND(lon_nd,6)=ROUND(121.065399,6)) OR
    (ROUND(lat_nd,6)=ROUND(14.653880,6) AND ROUND(lon_nd,6)=ROUND(121.066532,6)))
AND na.idelm_na = nd.idelm_nd AND adr.id_adr = na.idadr_na;

What it does is that it returns the adr.road_adr associated to the coordinates(lat,lon). What it returns is ordered by idelm_na by default. Is there a way to rewrite this code that will return the result based on the order of the OR arguments/parameters? I can use UNION ALL with individual SELECT statements, but I think this is too slow. I hope someone can help me here. Thanks!

Answer 1

First, do not use the comma-separated syntax for Joins. Use the ISO standard. Second, to achieve what you want, you need to build the query differently. You can achieve what you want if you supply a sort order to the inputs. In addition to providing the ability to do your sort, you also make it easier to build the list of inputs:

Select idelm_na AS ID, nd.lat_nd AS lat, nd.lon_nd AS 'lon' , adr.road_adr AS 'road' 
From node_nd As ND
    Join node_address As NA
        On NA.idelm_nd = ND.idelm_na
    Join address_adr As ADR
        On ADR.id_adr = NA.idadr_na
    Join    (
            Select 1 As Rnk, 14.654733 As Lat, 121.058403 As Lon
            Union All Select 2, 14.654791, 121.062386
            Union All Select 3, 14.654791, 121.064343
            Union All Select 4, 14.654754, 121.064403
            Union All Select 5, 14.654648, 121.064450
            Union All Select 6, 14.653869, 121.064798
            Union All Select 7, 14.653865, 121.065399
            Union All Select 8, 14.653880, 121.066532
            ) As Z
        On Round(lat_nd, 6) = Z.Lat
            And Round(lon_nd, 6) = Z.Lon
Order By Z.Rnk

Answer 2

You can add an "ORDER BY" clause to the SELECT statement:

SELECT idelm_na AS ID, ... WHERE ... ORDER BY lat_nd, lon_nd;

This will sort the results first by lat_nd, then by lon_nd.