比如如下的SQL语句：
select sum(f1),f2 from (
select a.a1 as f1, a.a2 as f2, a.a3 as f3 from a
left join select b.b1 as f1,b.b2 as f2, b.b3 as f3 from b
union all
select c.c1 as f1,c.c2 as f2, c.c3 as f3 from c where c.c1 < 100
) group by f2
要程序实现给查询语句添加条件 a.a1 > 10、b.b2 = 5 、c.c1 < 100达到下面的效果：
select sum(f1),f2 from (
select a.a1 as f1, a.a2 as f2, a.a3 as f3 from a
left join select b.b1 as f1,b.b2 as f2, b.b3 as f3 from b
where a.a1 > 10 and b.b2 = 5
union all
select c.c1 as f1,c.c2 as f2, c.c3 as f3 from c where c.c1 < 100
) group by f2
怎么实现这样的效果请指点一下。
已有的SQL文如果可以作为一个String取到的话，那就好办了。
按照你自己写出来的那样，把那个String断开，在union all的前面插入你想要的条件。再把这个修改过的SQL文执行下就好了。
如果不能取到的话，那基本就没戏了。
除非让那条SQL文事先埋下用于扩展的参数。
比如类似下面
[code="sql"]
...
left join select b.b1 as f1,b.b2 as f2, b.b3 as f3 from b
#{将来可能要添加的条件参数}
union all
...
[/code]
就是一个SQL语句的动态拼装么。根据传进来的条件，动态生成SQL语句。只要搞清楚哪些是不变的，哪些是变得。自然就写出来了。