你如何编写一个易于理解（/可维护）的搜索功能？也许以模块化的方式？

Every time I see a search function, the code behind it is a mess. Several hundreds of lines, spaghetti code, and almost ALWAYS as one huge method. A programming language (Java/C#/PHP/etc) is used to construct one big fat SQL query. Many, many if else's. Every time I see a search function, the code be