java - 如何使用java正则表达式将查询列表sql转换为查询计数sql

Question

我想删除 order by在sql中，并转换

select a,b,c from进入select count(*) from

<小时/> select uid, uname from user order by uid

=>

select count(*) from user

<小时/> select uid, (select depname from department t01 where t02.depid = t01.depid ) from user t02 order by uid

=>

select count(*) from user t02

<小时/> select uid, '('||uname||')' from user

=>

select count(*) from user

<小时/> select uid from (select uid,rownum as row_num from user order by uid) where row_num < 10 order by uname

=>

select count(*) from (select uid,rownum as row_num from user order by uid) where row_num < 10

<小时/> 如何使用 java regex 做到这一点？

select uid, uname from user order by
hibernate可以将其转化为页面查询select uid, uname from user order by limit xxxx自动执行，我们可以得到一个列表。

那么如果我们执行select count(*) from user ，我们将获得用户数量。

pageNo , pageSize是我自己设置的，pageNum是 record_count/pageSize 。我希望得到table/grid的所有数据通过一条sql，但我不知道如何将查询列表sql转换为查询计数sql。

Answer 1

假设 order by 位于最后，您可以使用

query = query
 .replaceFirst("(?is)\\sorder\\s+by\\s.*$","");
 .replaceFirst("(?is)^\\s*select\\s.*?from\\s","select count(*) from ");

但是，这不太合适。分析 SQL 查询需要语法分析，这超出了正则表达式的范围。我给出的示例将失败

select ... from ... where title = 'I want to order by my cat'

这是一个简单的计数器示例，但您可以想象更复杂的 SQL 查询。