1.If I knew her phone number, I would call her.
2.Did I know her phone number, I would call her.
One of my grammar books say 2 is grammatically. Is it?
I read a lot of American crime novels, and I've become aware in recent years of characters speaking colloquially omitting if in conditional sentences.
'You wanna keep your kneecaps intact, asshole, stay outta my face.'
I just taught 1st, 2nd, and 3rd conditionals in an intermediate class, and the rule in the book was IF can only be omitted in the third conditional, like Raymott said.
You can instead use, Had I known and Otherwise.
If he comes/came - should he come
If he came - were he to come
If there is no pain, there can be no gain - No pain, no gain
If you don't stop, I'll shoot - Stop, or I'll shoot.
.....................................T Try to escape, and I'll shoot.