有用的SQL语句

1：导入数据
imp80 file=d:tempdbfile1.dmp full=n fromuser=yh1 touser=yh2;

2：多表更新
update table1 a set a.column1=(select b.column1 from table2 b
where a.column2=b.2column2)
where a.column3 is not null;