这是我在学习sql时，发现非常容易出错的问题。平时都把点点滴滴记录下来了。便于在写语言时，出错后对照下这些语法，很快就能解决问题-This is my sql in the study, we found that the problem is very easy to make mistakes. Usually regarded bits and pieces recorded. Easy to write language, grammar mistakes, these were soo