看到有人说 having子句不能单独使用

[lyyscf]

论坛上看到有人说having子句不能单独使用，后面还有很多人赞同，我表示不能忍了..

例子，举个最简单的

select 1 from dual having count(1) = 1;

再说一个用途

--书
create table book as
select 1 id,'小说A' name from dual union all
select 2 , '小说B' from dual union all
select 3 , '小说C' from dual;

--用户读那本书
create table book_reader as
select 111 id, 1 bookid from dual union all
select 112 , 1 from dual union all
select 113 , 2 from dual ;

--只有一个用户读的书
select *
  from book a
 where exists (select 1
          from book_reader b
         where a.id = b.bookid 
     having count(1) = 1);

[睿智天成]

SF

[lbq794619111]

可以的，没问题，顶起