data a;
        input a $3. b $3.;
        cards;
ABCDEF
;
run;

data b;
        set a;
        D=CATQ(" ",A,B);
run;

————————————————————
跑出来不是你那个结果哦

原来的数据是A = "Single"
B = "Blank Between"
结果是 Single "Blank Between"

这本来就是CATQ的用法啊，
CATQ Function
Concatenates character or numeric values by using a delimiter to separate items and by adding quotation marks to strings that contain the delimiter.
根据你的描述，应该是用CATS，
CATS Function
Removes leading and trailing blanks, and returns a concatenated character string.
其实，还有CATT和CATX另外两个，
CATT是只管移除掉trailing blanks，然后和CATS用法一致，
CATX和CATQ用法差不多，要用分隔符把各个字符分开，但是他同时也要去掉leading和trailing的空格

data _null_;
a='abc';
b='efg';
a1=' abc ';
b1=' efg ';
c1=cats(a,b);
c2=catq(' ', a,b);
c3=catt(a1,b1);
c4=catx(' ', a1, b1,'C');
c5=catq(' ', a1, b1, 'C');
put c1;
put c2;
put c3;
put c4;
put c5;
run;

catq(" ",A,B) 因为modifiers是必须有的，而delimiter是选择性有的，我就把括号里面的“ ” 当成modifiers,然后就怎么也看不懂。按照你的意思 “ ” 应该是delimiter，所以含有空格的加上引号。是吧

应该是这个意思 ，Concatenates character or numeric values by using a delimiter to separate items and by adding quotation marks to strings that contain the delimiter.