SQL Server interview Questions on JOIN’s

This SQL Server interview question was asked in Capgemini Mumbai to one of our readers. In case you are new SQL Server joins you can see our video which explains 4 important SQL Server joins

 

Let’s say you have two tables with following structure and data.

table

Question – How many rows will be returned in case of inner query?Answer – 24

Question – Why 24?
Answer – Because in case of inner join every row in a left table is matched with every row in a second table and when that record will be shown in the screen.

Question – Then how it is different from Cross join?
Answer – In cross join no match condition will be provided. We straight forward write Select * from Table1, Table2. And result will Number of rows in left table*number of rows in right table whereas for inner join its matching records. In our current case every record in the left table is matching with the every row in right table and hence it is behaving like cross join.

Question – Is it possible to provide more than one match condition while writing inner join query?
Yes.

Question – How many columns will be returned when you write a query Select * from Table1, Table2
Its 4

Why?
Because Table1 has 2 columns and Table2 has 2 columns and in query we are using * means Table1 Columns + Table 2 columns 

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