if引导的虚拟语气if条件一定在主句前吗

if 引导的虚拟句有固定形式：if + 主语 + 过去式动词 ,
比如：
If you were at the meeting,it would have gone a lot more smoothly.
If I asked you for a date,would you say yes?
If John were here,he would be very annoyed.
If the weather were better,we would be going to the park.
If I wanted a car,I would have bought one.