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Match the SQL subquery operator with its function

Checks if a subquery returns any rows

Keyword is commonly used to introduce a subquery

Compares a value with the result of a subquery that returns multiple rows

Checks if a subquery returns no rows

Which type of subquery is evaluated for each row processed by the outer query?

Non-correlated subquery

Scalar subquery

Nested subquery

Correlated subquery

Which operator is used ...

(match the appropriate)

to compare for equality a single value with the result of a subquery?

to check if a subquery returns no rows?

to compare by more/less a value with the result of a subquery that returns a single column and a single row?

Which type of subquery is executed once for the entire outer query?

Scalar subquery

Non-correlated subquery

Correlated subquery

Nested subquery

It will not bring the customers that they have never put an order.

Assuming that we have 2 tables - customers and orders:

Assuming the following query

select * from customers join orders on orders.customer_id = customers.customer_id;

True

False

Which of the following is not true about NATURAL JOINs?

Natural joins are not based on primary/foreign keys

Natural join is based on all columns in two tables having same name

It selects rows from the two tables having different values in the matched columns

If columns having same names have different data types, it returns error

Which of the following is NOT a commonly accepted rule for joining multiple tables?

It is recommended that aliases be keywords to keep the statement uniform throughout the query

It is recommended that joins between tables are based on Primary/Foreign keys

Put join conditions before other conditions in the WHERE clause when using implicit join

Any table listed in a join condition MUST exist in the FROM clause when using implicit join

A UNION query is which of the following?

Combines the output from multiple queries and does not include the same number of columns

Combines the output from multiple queries and must include the same number of columns

Combines the output from no more than two queries and must include the same number of columns

Combines the output from no more than two queries and does not include the same number of columns

What type of join is needed when you wish to include rows that do not have matching values?

INNER JOIN

SELF JOIN

OUTER JOIN

CROSS JOIN