CH 2B- Introduction to Structured Query Language

Question 1

techniques for querying data from multiple tables

Answer 1

– The SQL subquery

– The SQL join

Question 2

SQL subquery

Answer 2

– A nested query
– A query within a query

*only the columns of the top level query can be displayed in the query results!

• Multiple subqueries can be used to process three or even more tables.
• All parts if the SQL SELECT statement syntax can be applied to the table displaying the results of an SQL query using subqueries.

**can only be used to retrieve data from
the “top table.”

Question 3

SQL join operation

Answer 3

used to combine parts or all of two or more tables.

a) Explicit join ─ the SQL JOIN operator is used as part
of the SQL statement.

b)Implicit join ─ the SQL JOIN operator is not used as
part of the SQL statement.

**can be used to obtain data from any number
of tables, including the “top table” of the subquery.

Question 4

SQL CROSS JOIN

Answer 4

-combines each row in one table with every row in another table.

Question 5

Implicit SQL INNER JOIN

Answer 5

-selecting rows by matching by the primary key values
of one table with the foreign key values of a second table.

does not appear in the SQL statement, this is an implicit join.

Question 6

Explicit SQL INNER JOIN

Answer 6

Selecting rows by matching by the primary key values of one table with the foreign key values of a second table

*does appear in the SQL statement,
this is an explicit join.

Question 7

SQL ALL Keyword

Answer 7

-wanted the duplicated rows to be displayed in the query output

Question 8

SQL INTERSECT Operator

Answer 8

-In both

Question 9

SQL EXCEPT Operator

Answer 9

-Excluding one option