Compare two datasets(different sizes) for closest point- code attempted

There have been an number of posts comparing matrices or associating closest points within two matrices. My problem involves two datasets of coordinates x y z. One dataset* A* is about 26300 rows long and dataset B is 26500 rows long. A and B are type double. Some of the coordinates in A are exactly the same as in B. Some of the coordinates in A are within 0.01mm of B. Some of the coordinates in A have the same value of x, y or z meaning that simply comparing one column of the coordinates in A and B is not possible. Some of the coordinates in A are not in B.

My challenge is to identify the coordinates in B that are in A by either finding an exact match in B or by finding points within 0.01mm of coordinates in B. I need to retain a sense of row order- the coordinates are associated to other elements in a larger dataset.

This is my attempt so far. It seems to work but isn't very elegant.

% A is the smaller dataset
% B is the larger dataset

[xi,yi]=size(A);
[xj,yj]=size(B);

C=[];
Out=[];
D=[];
E=[];
false=[];

for i=1:xi;
    C=find(A(i,3)==B(:,3));
    if length(C)==1;
        D=A(i,1)-B(C,1);
        E=A(i,2)-B(C,2);
        if D>=-0.01 & D<=0.01
            Out(i,:)=cat(2,A(i,:),B(C,:),C);
        elseif D<-0.01 | D>0.01
            Out(i,:)=0;
            [x1,y1]=size(false);
            false(x1+1,:)=cat(2,i,C);
        end
    elseif length(C)>1;
        [x2,y2]=size(C);
        for k=1:x2;
            D=A(i,1)-B(C(k),1);
            E=A(i,2)-B(C(k),2);
            if D>=-0.01 & D<=0.01
                T=1
            elseif D<0.01 | D>0.01
                T=0
            end
            if T==1
                [x5,y5]=size(U)
                U(x5+1,:)=C(k);
            end
        end
        if length(U)==1
            Out(i,:)=cat(2,A(i,:),B(U,:),U);
        elseif length(U)>1
            [x3,y3]=size(U);
            for l=1:x3
                D=A(i,1)-B(U(l),1);
                E=A(i,2)-B(U(l),2);
                if E>=-0.01 & E<=0.01
                        S(l)=1
                elseif E<0.01 | E>0.01
                        S(l)=0
                end
            end
            V=find(S==1);
            if length(V)==1
                Out(i,:)=cat(2,A(i,:),B(U(V),:),U(V));
            elseif length(V)>1 | length(V)<1
                Out(i,:)=0;
           end
        end
    elseif length(C)<1
        Out(i,:)=0;
    end
    U=[];
    V=[];
    T=[];
    S=[];
end

Advice welcome on how I can improve this code

Mel