If I had a good job, I'd be rich.
This is an imaginary present situation, with its present result.
If I had studied medicine, I'd have become a doctor.
This is an imaginary past situation, with its past result.
A mixed conditional gives a situation and result - but one is in the past, and the other is in the present. For example:
If I had studied medicine at university, I'd be rich now.
This is an imaginary past situation, with an imaginary presentresult.
|Imagined Past Situation||Imagined Present Result|
|if + had(n't) + past participle||would(n't) + verb (infinitive)|
|If we had taken the car,||we wouldn't be late.|
|Imagined Present Situation||Imagined Past Result|
|if + past simple||would(n't) + have + past participle|
|If I didn't love him,||I wouldn't have marriedhim.|
As with all other conditionals, it doesn't matter which half of the sentence comes first:
If I didn't love him, I wouldn't have married him.
= I wouldn't have married him if I didn't love him.
From: The Tiny TEFL Teacher