What Would Have Happened
The third, or 'past', conditional is used to imagine past outcomes different than what actually took place. This conditional is used to express what would have been different if a person had done something differently.
'If' clause - past perfect + , + result clause - would + have + verb (conditional perfect tense)
"If they had known our recipe costing formula, they would have implemented it."
She wouldn't have agreed with her business acquaintances if she'd know the whole story.
She would be there now if her boss had wanted to rent one of our conference centers.
Where would you have eaten if you had wanted gourmet-type dining?
Examples of Past Unreal Outcomes
Do not use a comma, when placing the result clause first.
She would have trained as a food service professional if she had got the job.
She would have prepared desserts if Susan had thrown the party.