DBMS Q6

Clause that divides the rows returned from the SELECT statement into groups

• GROUP BY

• ORDER BY

• BETWEEN

• NOT IN

  верно

Choose correct order of execution of the SQL statement

• FROM->WHERE->GROUP BY->HAVING->SELECT->DISTINCT->ORDER BY->LIMIT

• LIMIT ->FROM->WHERE ->HAVING->SELECT->DISTINCT->ORDER BY->GROUP BY

• SELECT->DISTINCT->ORDER BY->LIMIT-> FROM->WHERE->GROUP BY->HAVING

• 
  HAVING->SELECT->DISTINCT->ORDER BY->LIMIT ->FROM->WHERE->GROUP BY

SQL query nested inside a larger query

• Subquery

• Joined query

• 
  Superquery

• Supporting guery

Choose correct statement

• A subquery can have multiple columns in the SELECT clause, unless only one column in the main query for the subquery to compare its selected columns

• 
  Subqueries must be enclosed within parentheses

• An ORDER BY can be used in a subquery, although the main query can’t use an ORDER BY

• 
  The BETWEEN operator can be used with a subquery; however, the BETWEEN cannot be used within the subquery

Choose correct syntax of using subqueries with IN operator

• expression IN (subquery)

• expression IN subquery

• 
  expression IN * subquery

• 
  subquery && expression IN()

Choose correct statement

• 
  A row subquery is a subquery that returns a single row and more than one column value

• 
  A row subquery is a subquery that returns a single column and more than one rows

• A row subquery is a subquery that returns a single column and only one row

• A row subquery is a subquery that returns more than one columns and more than one rows

What is true when using subqueries with EXISTS operator?

• If it returns at least one row, the result of EXISTS is true

• 
  The result of EXISTS is true only if it returns multiple rows

• The result of EXISTS is true only if it returns one row

• Only if it returns more than one row, the result of EXISTS is true

What is a correlated subquery?

• 
  is a subquery that contains a reference to a table (in the parent query) that also appears in the outer query

• 
  is a subquery that returns a single row and more than one column value

• any subquery that returns more than one row

• 
  is a subquery that returns a single column and only one row

Choose wrong statement about subqueries with IN operator

• The result of IN is true if any equal subquery row is found

• The result is “false” if no equal row is found (including the case where the subquery returns no rows)

• If the left-hand expression yields null, or if there are no equal right-hand values and at least one right-hand row yields null, the result of the IN construct will be null, not false

• If the left-hand expression yields null, or if there are no equal right-hand values and at least one right-hand row yields null, the result of the IN construct will be false, not null

Choose an operator that compares the value to each value returned by the subquery

• ANY

• ALL

• NOT IN

• SOME