when i learned a local Chinese restaurant needed a waiter who could work in the evening该句子不就有两个谓语了嘛?learn和need
此句其实有三个谓语动词,分别是:learned, needed 和 (could) work;
learned 是 when 引导的时间状语从句的谓语动词, needed 是 learned 后面 that(that被省略) 引导的宾语从句的谓语动词,而 (could) work 则是修饰先行词 a waiter 的定语从句 who could work in the evening 中的谓语动词。
一个简单句除了并列谓语外,的确是只能有一个谓语动词,但是并列句和主从复合句并非如此,其实是有几个句子就有几个谓语动词。