A conditional consist of two clauses: the condition or if-clause and the main or result clause. Depending on the meaning we try to convey we have many different conditionals at our exposal to express ourselves clearly.
Mixed conditionals are those unreal conditional sentences whose time in the if-clause is different than the time in the main-clause.
The most common mixed conditional is a condition in the past with a result in the present.
Example: If I had been a singer, I would be rich!
The If clause is in the 3rd conditional, so it’s an unreal past, and ‘would be’ (2nd conditional) is an unreal present.
Past Condition / Present Result
The first one has a condition in the past and a present result. We use it to express that if something had been different in the past there would be a present result.
The structure is: If + past perfect, would (could, might) + infinitive.
Present Condition / Past Result
We use it to express that due to certain present conditions something already happened in the past.
The structure is: If + past simple, would (could, might) have + past participle.