Did you have lunch? ve Have you had lunch? arasındaki fark nedir?Sadece örnek cümleler vermekten çekinmeyin.

They mean similar things.

However, I feel the second question, 'Have you had lunch?' implies that the person asking wants to go out for lunch with you if you haven't already had lunch.

'Have you had lunch?'
'No, not yet.'
'Great, would you like to join us for lunch?'

'Did you have lunch?'
'No, they canceled our lunch date.'
'That's too bad.'

Personally, I feel as though 'Did you...' is asking past tense.
'Have you had...' seems more present tense.

Like leesheer said, they are pretty much the same.