网站的整站搜索SQL语句怎样写？
比如我有：products表，news表，about表，case表等等，输入关键字后，怎么写SQL语句？
[最优解释]
select col from products where col like '%关键字%'
union all
select col from news where col like '%关键字%'
union all
select col from about where col like '%关键字%'
union all
select col from case where col like '%关键字%'
