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Multiple Choice Questions - SQL Joins & Nulls

Multiple Choice Questions - SQL Joins & Nulls

1. When there are null values in the columns of the tables being joined, the null values . . . . . . . . each other.

A) match
B) do not match

2. When joining on a nullable column, remember that the equality operator returns . . . . . for Null = Null.

A) False
B) True
C) Error
D) Warning

3.
Table t1:        
tvalue
0000
1111
Null
Null


Table t2:        
tvalue
Null
1111
2222
Null

Which of the following query / queries will return result with "Nulls" including:

A) 
Select a.tvalue,
b.tvalue
from t1 a
inner join t2 b
on a.tvalue = b.tvalue;
B) 
Select a.tvalue,
b.tvalue
from t1 a
join t2 b
on a.tvalue = b.tvalue;
C) 
Select a.tvalue,
b.tvalue
from t1 a
full outer join t2 b
on a.tvalue = b.tvalue;
D) 
Select a.tvalue,
b.tvalue
from t1 a
left outer join t2 b
on a.tvalue = b.tvalue;
4. Outer joins (in SQL Server) do not use existing NULL values for matching. They produce NULL values when a match doesn't exist.

A) True
B) False

5. In SQL Server as the full outer join includes the rows that are equi-joined from both tables, plus the remaining unmatched rows from the first and second tables, NULLs are added to the unmatched rows . . . . . . . . .

A) on left side
B) on right side
C) on both sides
D) None of above

Answers