Tagrem Corp interview questions

They asked me to explain a real-time scenario where I used SQL joins to solve a business problem."

1)Explain indexes in mysql, its drawback, when not to use, 2)query to find tables starting with 'G' 3)parent private constructor getting called in child class 4)traits, what happens when 2 traits have same method, how to resolve 5)clone object and assigned new value to both the objects 6)inheritance, interface 7)can multiple catch be there for single try 8)difference between define and constant