select a.*,b.计划数15,b.分数线15,b.名次号15 from 2014理科三批 as a,2015理科三批 as b where allt(b.代码)=allt(a.代码) and ISNULL(b.科类)=.f. into dbf ls
以下是引用sylknb在2016-5-26 16:58:32的发言：
1).
SET null OFF
SET NULLDISPLAY TO " "
select a.*,b.* from 2015理科三批 as a FULL join 2014理科三批 as b on a.代码=b.代码
此时完全連接时没有null,只是空格
2).
SET null OFF
SET NULLDISPLAY TO " "
select a.*,b.* from 2015理科三批 as a FULL join 2014理科三批 as b on a.代码=b.代码 into table ls
use ls
brow
就出现了unll
当退出fox后再进入时ls表出现了null
1).
SET null OFF
SET NULLDISPLAY TO " "
select a.*,b.* from 2015理科三批 as a FULL join 2014理科三批 as b on a.代码=b.代码
此时完全連接时没有null,只是空格
2).
SET null OFF
SET NULLDISPLAY TO " "
select a.*,b.* from 2015理科三批 as a FULL join 2014理科三批 as b on a.代码=b.代码 into table ls
use ls
brow
就出现了unll
当退出fox后再进入时ls表出现了null
SET null OFF
SET NULLDISPLAY TO " "
只是在显示的时候，遇到 NULL时，显示""，并不是在数据库中把NULL 改为 ""
IIF(ISNULL(A.*),0,A.*)我觉得有错误的，反正我没用过，我刚才测试了1下，也报错误的。
我一般是这样写
USE g:\abcd\2014理科三批.dbf IN 0 ALIAS lk2014
SELECT lk2014
*BROWSE
USE g:\abcd\2015理科三批.dbf IN 0 ALIAS lk2015
SELECT lk2015
*BROWSE
SELECT IIF(ISNULL(a.计划数15),0,a.计划数15) as [计划数15],IIF(ISNULL(a.分数线15),0,a.分数线15) as [分数线15],IIF(ISNULL(a.名次号15),'',a.名次号15) as [名次号15],b.* ;
from lk2015 as a FULL join lk2014 as b on a.代码=b.代码
只写了1部分，，，，
