手工把你的2个SQL语句格式化一下以后create view kanasselect gno, name, unit, ( select sum(amount) from goods_in where goods_in.gno=goods.gno )- ( select sum(amount) from goods_out where goods_out.gno=goods.gno ) total from goodscreate view kanas select gno, name, unit, ( select sum(amount) from goods_in group by gno having goods_in.gno=goods.gno )- ( select sum(amount) from goods_out group by gno having goods_out.gno=goods.gno ) total from goods;发现差异在于，后面一个的 子查询里面 having 使用的不正确。

select sum(amount) from goods_in group by gno having goods_in.gno=goods.gno一般 having 是用于针对 分组统计后 的数据，进行进一步筛选的处理。

例如having sum(amount) > 100这种，在分组之前，无法用 WHERE 语句来筛选的。

而你这个SQLhaving goods_in.gno=goods.gno这个 goods_in.gno=goods.gno 是不需要分组以后，才能作筛选处理的。

分组处理以前的 where 就可以处理了。