lnPointX=300
lnPointY=200

lnMinDistance=-1
lnMinPointId=0
scan
  lnDistance=sqrt((lnPointX-coordX)^2+(lnPointY-coordY)^2)
  if lnMinDistance=-1 or lnDistance<lnMinDistance
    lnMinDistance=lnDistance
    lnMinPointId=PointId
  endif
endscan

CREATE CURSOR points (PoindId i, coordX i, coordY i)

FOR i=1 TO 20
    INSERT INTO points VALUES (i, INT(500*RAND()),INT(500*RAND()))
ENDFOR

lnPointX=300  
lnPointY=200  

SELECT TOP 1 *, sqrt((lnPointX-coordX)^2+(lnPointY-coordY)^2) as distance ;
    FROM points;
    ORDER BY distance

index on bintoc(coordx)+bintoc(coordy) tag xy
set Near On
seek bintoc(nPointX)
seek bintoc(coordx)+bintoc(nPointY)
lnDistance=d()
seek bintoc(nPointX-lnDistance)
scan rest while coordX<=nPointX+lnDistance for lnDistance>d()
    lnDistance=d()
    lnMinPointId=pointId
endscan

function d
return sqrt((nPointX-coordX)^2+(nPointY-coordY)^2)

CREATE CURSOR points (PoindId i, coordX i, coordY i, square i)  
    
FOR i=1 TO 20  
    INSERT INTO points (PoindId, coordX, coordY) VALUES (i, INT(500*RAND()),INT(500*RAND()))  
ENDFOR  
replace all square with (coordX^2 + coordY^2)

lnPointX = 300
lnPointY = 200
lnSquare = lnPointX^2 + lnPointY^2

SELECT TOP 1 *, m.lnSquare + square - 2*(coordX*m.lnPointX + coordY*m.lnPointY) as SquareDist ;  
FROM points ;  
order by 2 

SELECT TOP 1 *, ((m.lnPointX - coordX)^2 + (m.lnPointY - coordY)^2) as SquareDist ;  
FROM points ;  
order by 2

SELECT TOP 1 *, (abs(m.lnPointX - coordX) + abs(m.lnPointY - coordY)) as ModuleDist ;    
FROM points ;    
order by 2

select * from points ;
where between(coordX,lnPointX-lnMaxX,lnPointX+lnMaxX) ;
and between(coordY,lnPointY-lnMaxY,lnPointY+lnMaxY) ;
into cursor Temp

SELECT TOP 1 *, (abs(m.lnPointX - coordX) + abs(m.lnPointY - coordY)) as ModuleDist ;      
FROM Temp ;      
order by 2

CREATE CURSOR test (x int, y int, r n(12,2) DEFAULT SQRT(x**2 + y**2))

INSERT INTO test (x, y) VALUES (1 , 1)
INSERT INTO test (x, y) VALUES (1 , 2)
INSERT INTO test (x, y) VALUES (2 , 1)
INSERT INTO test (x, y) VALUES (2 , 2)
INSERT INTO test (x, y) VALUES (3 , 3)

m.x = 3.5 && точка которую ищем
m.y = 1 && точка которую ищем

m.r = SQRT(m.x**2 + m.y**2)  && длина вектора для искомой точки

SELECT TOP 1 a.r, x, y FROM (select ABS(m.r - r) as r, x, y FROM test ) a ORDER BY a.r