数据库编程的鼠标“增加”事件不能成功

Question

string booknum,bookname,auther,publisher
string publish_time, price,store
booknum=trim(sle_1.text)
bookname=trim(sle_2.text)
auther=trim(sle_3.text)
publisher=trim(sle_4.text)
publish_time=trim(sle_5.text)
store=trim(sle_6.text)
price=trim(sle_7.text)

if len(booknum)=0 then
messagebox("书号","请输入书号!")
sle_1.setfocus()
return
end if
if len(booknum)<>6 then
messagebox("书号","书号应为6位数!")
sle_1.setfocus()
return
end if
if len(bookname)=0 then
messagebox("书名","请输入书名!")
sle_2.setfocus()
return
end if
if len(auther)=0 then
messagebox("作者","请输入作者!")
sle_3.setfocus()
return
end if
if len(publisher)=0 then
messagebox("出版社","请输入出版社!")
sle_4.setfocus()
return
end if
if len(publish_time)=0 then
messagebox("出版日期","请输入出版日期!")
sle_5.setfocus()
return
end if
if len(price)=0 then
messagebox("存量","请输入存量!")
sle_6.setfocus()
return
end if
if len(store)=0 then
messagebox("单价","请输入单价!")
sle_7.setfocus()
return
end if

select shuhao into :booknum from t_bookmanage where shuhao=:booknum;
if SQLCA.SQLCode = 0 then
messagebox("增加","此书号已经存在")
sle_1.text=""
sle_1.setfocus()
return
end if
select shuming into :bookname from t_bookmanage where shuming=:bookname;
if SQLCA.SQLCode = 0 then
messagebox("增加","此书名已经存在")
sle_1.text=""
sle_1.setfocus()
return
end if
insert into t_bookmanage(shuhao,shuming,zuozhe,chubanshe,chubanriqi,chuliang,danjia)
values(:booknum,:bookname,:auther,:publisher,:publish_time,:store,:price);
if SQLCA.SQLCode=0 then
messagebox("增加","此图书添加成功")
else
messagebox("增加","此图书未能增加成功!")
end if
sle_1.text=""
sle_2.text=""
sle_3.text=""
sle_4.text=""
sle_5.text=""
sle_6.text=""
sle_7.text=""
sle_1.setfocus()