Chapter 18 - Introduction to SQL

Question 1

What is SQL?

Answer 1

» SQL is a declarative language used to query and update tables in a relational database

Question 2

What does the SELECT command do?

Answer 2

» Used to extract a collection of fields from a given table

Question 3

What does the FROM command do?

Answer 3

» Specifies from which table the data will come from

Question 4

What does the WHERE command do?

Answer 4

» Lists the search criteria

Question 5

What does the ORDER BY command do?

Answer 5

» List the fields that the results are to be sorted on

Question 6

What is one key feature to remember about the ORDER BY command?

Answer 6

» Default order is always ASC

Question 7

What are the 2 types of commands in the ORDER BY statement?

Answer 7

» ASC
» DESC

Question 8

What does the = command mean?

Answer 8

» Equal to
» Such as Title = “Death note”

Question 9

What does the != command mean?

Answer 9

» Not equal to

Question 10

What does the >= command mean?

Answer 10

» Greater than or equal to

Question 11

What does the <= command mean?

Answer 11

» Less than or equal to

Question 12

What does the IN command do?

Answer 12

» Equal to a value within a set of values

Question 13

What is the LIKE command?

Answer 13

» Similiar to

Question 14

What does the BETWEEN..AND command mean?

Answer 14

» Within a range
» Such as Datepublish BETWEEN 01 AND 31

Question 15

What is the IS NULL operator?

Answer 15

» Field does not contain a value

Question 16

What is the standard structure of a SQL query?

Answer 16

» SELECT
» FROM
» WHERE
» ORDER BY

Question 17

What is the * operator?

Answer 17

» A wild card, selects all the fields of records

Question 18

What are the commands to combine data from two or more tables, by only specifying which table the data is held in?

Answer 18

» Using the syntax:
» tablename.fieldname
» Then use multiple instances of this syntax to combine the tables

Question 19

What is one thing to remember when joining data from two or more table?

Answer 19

» The table name is optional unless the field name appears in more than one table

Question 20

How can you provide a link between tables in SQL?

Answer 20

» Using a condintion in the WHERE clause, such as eg..
» WHERE song.artistID = Artist.ArtistID

Question 21

What is an alternative method of combining rows from two or more tables?

Answer 21

» Using the SQL JOIN command

Question 22

When can the JOIN command be used?

Answer 22

» Can be used to combine data from two or more tables by specifying a common field between them

Question 23

What is the main command of the JOIN operator?

Answer 23

» JOIN tablename
» ON tablename.field = tablename.field
» Note the table name is the other table which is not in the FROM statement

Question 24

What is one key thing to remeber after using the JOIN command?

Answer 24

» Remember to specify the table where the field is coming from
» Usually just do the table in which it is in the FROM statement then dot the record which links the 2 tables

Question 25

What is the main overall structure of the SQL query when there is a JOIN command?

Answer 25

» SELECT
» FROM
» JOIN
» ON
» WHERE