pb中有错误 请高手指点

string ls_kcbh,ls_kcmc,ls_pym
string ls_select
string is_sql

ls_kcbh=sle_1.text
ls_kcmc=sle_3.text
ls_pym=sle_2.text

ls_select=""
if not isnull(ls_kcbh) and ls_kcbh <> "" then
ls_kcbh= " % " + ls_kcbh + " % "
ls_select =ls_select + " 课程.课程号 like '"+ls_kcbh + "'"
end if

if not isnull(ls_kcmc) and ls_kcmc <> "" then
ls_kcmc= " % " + ls_kcmc + " % "
if ls_select = "" then
ls_select =ls_select + " 课程.课程名称 like '"+ls_kcmc + "'"
else
ls_select =ls_select + " and 课程.课程名称 like '"+ls_kcmc+ "'"
end if
end if

if ls_select = " " then
dw_1.retrieve()
else
ls_select = is_sql + " and " +ls_select
dw_1.SetSQLSelect(ls_select)
dw_1.retrieve()
end

(1)你的is_sql根本就没有值，应该是string is_sql="select 表中你要显示的字段名 from 表名 where "
(2)ls_kcbh= " % " + ls_kcbh + " % " 和 ls_kcmc= " % " + ls_kcmc + " % " 应该改成 ls_kcbh="'"+"%"+ls_kcbh+"%"+"'" 和 ls_kcmc="'"+"%"+ls_kcmc+"%"+"'" ,因为使用Like时格式是like '%条件%'，然后这两个表达式最好不要含有空格，否则可能查不出你想要的结果！
（3）然后 ls_select =ls_select + " 课程.课程号 like '"+ls_kcbh + "'"
和ls_select =ls_select + " 课程.课程名称 like '"+ls_kcmc + "'" 和
ls_select =ls_select + " and 课程.课程名称 like '"+ls_kcmc+ "'"
中的最后一个+可以不要了。
（4）最后把正确的语句给你，测试正确的，你自己再试试！
string ls_kcbh,ls_kcmc,ls_pym
string ls_select="select 课程.课程号,课程.课程名称 from 课程 where "
string is_sql

ls_kcbh=sle_1.text
ls_kcmc=sle_3.text
ls_pym=sle_2.text

ls_select=""