非常感谢各位大侠的鼎力相助，我将HOPEWELL的代码做了延伸，可以使用到变量长度，FORMAT和INFORMAT长度，如下：

LIBNAME BEN02 "F:\TEMP";

DATA BEN02.TEMP1;
ATTRIB Date LENGTH = 8 FORMAT = 8.0 INFORMAT = Date10. LABEL = "1THIS IS THE DATE";
ATTRIB Y1 LENGTH = 4 FORMAT = 4.0 INFORMAT = 4.0 LABEL = "1THIS IS THE SIZE";
ATTRIB COLOR LENGTH = $8 FORMAT = $8. INFORMAT = $8. LABEL = "1THIS IS THE COLOR";
INPUT Date Y1 COLOR;
DATALINES;
11Jan2010 123        R       
12Jan2010 223        G       
13Jan2010 323        B
;
RUN;

DATA BEN02.TEMP2;
ATTRIB Date LENGTH = 8 FORMAT = 8.0 INFORMAT = Date10. LABEL = "2THIS IS THE DATE";
ATTRIB Y1 LENGTH = 8 FORMAT = 5.1 INFORMAT = 5.1 LABEL = "2THIS IS THE SIZE";
ATTRIB COLOR LENGTH = $50 FORMAT = $50. INFORMAT = $50. LABEL = "2THIS IS THE COLOR";
INPUT Date Y1 COLOR;
DATALINES;
15Jan2010 12.3        RED12       
16Jan2010 22.3        GREEN       
17Jan2010 32.3        BLUE2
;
RUN;

%MACRO COMBINE01(Mydatalib = , Mycomdata = );

PROC CONTENTS DETAILS DATA=&Mydatalib.._ALL_ OUT = WORK.VarList;
RUN;

    %LOCAL datasetsnms;
    PROC SQL /*NOPRINT*/;
            SELECT CATX(".",libname,memname) into: datasetsnms SEPARATED BY " "
        FROM sashelp.vmember
                WHERE LIBNAME = UPCASE("&Mydatalib") and MEMTYPE = "DATA";

                CREATE TABLE WORK.Mytablenull AS
                SELECT NAME, TYPE,
                                        MAX(LENGTH) AS LENGTH,
                                        MAX(FORMATL) AS FORMATL, MAX(FORMATD) AS FORMATD,
                                        MAX(INFORML) AS INFORML, MAX(INFORMD) AS INFORMD
                FROM        WORK.VarList
                WHERE LIBNAME = UPCASE("&Mydatalib") AND MEMTYPE = "DATA"
                GROUP BY        NAME, TYPE;
        QUIT;
        PROC SQL;
        DESCRIBE TABLE WORK.Mytablenull;
        QUIT;

    %LET Mycomsas = %SYSFUNC(PATHNAME(&Mydatalib))\Mycomcode.sas;
       
    DATA WORK.Mydatanull;
                FILE "&Mycomsas";
               
                SET WORK.Mytablenull END = Mylastobs;
                IF _N_ = 1THEN PUT "Data &Mydatalib..&Mycomdata;";
                IF TYPE = 1 THEN PUT  "ATTRIB" +1 NAME "LENGTH = " LENGTH "FORMAT = " FORMATL +(-1) "." FORMATD "INFORMAT = " INFORML +(-1) "." INFORMD ";";
                IF TYPE = 2 THEN PUT  "ATTRIB" +1 NAME "LENGTH = " "$" LENGTH "FORMAT = " "$" FORMATL +(-1) "." FORMATD "INFORMAT = " "$" INFORML +(-1) "." INFORMD ";";
       
                IF Mylastobs =1 THEN DO;
                        PUT " SET &datasetsnms;";
                        PUT "RUN;";
                END;
        RUN;
    %INCLUDE "&Mycomsas";
%MEND COMBINE01;

%COMBINE01(Mydatalib = BEN02, Mycomdata = Mycombined);

受教了，正在研究SAS

我也遇到了相同的问题，要合并三个数据库  数据库之间不同的变量出不来，跟楼主提问的情况一样。看了各位老师的宏，由于刚学SAS，实在看不懂该怎么弄的，现在着急合并中，各位大大，可以指教下么  我的QQ号是402776533