我想实现以下功能，在form1中的edit文本框中输入单号，保存时判断这个单号是否存在于另外三个表， 表table1,table2,table3中单号以不同字段表示，比如，dh1，dh2，dh3. 不知道该怎么写了。select count(1) as aNum from ( select dh1 from table1 where dh1=QuotedStr(edit1.text) union all select dh2 from table2 where dh2=QuotedStr(edit1.text) union all select dh3 from table3 where dh3=QuotedStr(edit1.text) ) as p
if not exists (select dh1 from table1 where dh1=QuotedStr(edit1.text)) select -1 else if not exists (select dh1 from table2 where dh1=QuotedStr(edit1.text)) select -2 else if not exists (select dh1 from table3 where dh1=QuotedStr(edit1.text)) select -3 else select 0
那就只要统计出来的aNum>=1即可了
单号存在于另外三个表中的任何一个都行！ 转换成delphi语言呢，用query组件，太笨了，初学者 with adoquery1 do begin close;sql.clear; sql.add('select count(1) as aNum from '); &nbs
