represents all possible combinations of rows in two or more tables
represents the combinations of matching rows from two or more tables
represents the rows from one table matched with rows from a second table; where this is not possible, the result row is filled with NULL s where the data from the second table would have been
none of the above
2:
A left join
represents all possible combinations of rows in two or more tables
represents the combinations of matching rows from two or more tables
represents the rows from one table matched with rows from a second table; where this is not possible, the result row is filled with NULL s where the data from the second table would have been
none of the above
3:
An equijoin :
represents all possible combinations of rows in two or more tables
represents the combinations of matching rows from two or more tables
represents the rows from one table matched with rows from a second table; where this is not possible, the result row is filled with NULL s where the data from the second table would have been
none of the above
4:
A correlated subquery is called this because
it correlates rows between tables
it correlates rows in a single table
it correlates two joins
it correlates the rows in an outer query with rows in an inner query
5:
The difference between the two queries marked 5.1 and 5.2 in the following text is that
there is no difference
they return different data
they return the same data but the left join (Query 5.1) is likely to execute faster
they return the same data but the subquery (Query 5.2) is likely to execute faster
Query 5.1:
select employee.name from employee left join assignment on employee.employeeID = assignment.employeeID where clientID is null;
Query 5.2:
select e.name, e.employeeID from employee e where not exists (select * from assignment where employeeID = e.employeeID);
