Sprint review is second last important ceremony in the sprint. The idea here is to get early feedback from customer and stakeholders. So team showcases here whatever they have completed in last 2 week’s time (assuming team is following 2 week sprint) and get feedback from customer.
Sometimes team may feel hesitant to showcase the incomplete work to customer, they may want to defer the sprint review also as they have not completed all the stories whatever they have committed in sprint planning. This situation becomes more difficult for Scrum Master to handle. He/She wants to have this ceremony happening in sprint duration only but team may not be ready for that, so how SM would handle this situations ?
I think it’s OK to showcase completed stories only. SM can have discussion with team and convince them of showcasing completed stories first and then can just talk about incomplete stories, what challenges team was facing and why could not complete the stories. May be can discuss the possible timeline to complete the stories and decide on when they can showcase the remaining incomplete stories.
Idea is not to hold the completed stories for showcase because of incomplete stories, get the feedback on completed stories and notify customer on incomplete work. Have the status transparent with customer and stakeholders.
Hope this will help you to guide your team on handling incomplete work in sprint review.