PL/SQL块   declare   begin    --SQL语句    --直接写的SQL语句(DML/TCL)    --间接写execute immediate <DDL/DCL命令字符串>     --select 语句         <1>必须带有into子句          select empno into eno from emp

select sum(price*qty) from books;select pub,sum(price*qty) from books group by pub;select pub,sum(price*qty) from books group by pub having sum(price)>50; select a1.count(a1) from aa group by a1 havi