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21.6. More SELECT Keywords

So far we have covered selecting the data from all fields from a table, from just one specified field, and from a list of fields.

Q-1: Match each SQL statement with what it does. Refer to previous SELECT examples.
• SELECT * FROM Tracks
• Returns the data from all fields (columns) from the Tracks table
• SELECT title FROM Tracks
• Returns the data from just the title field (column) from the Tracks table
• SELECT title, length FROM Tracks
• Returns the data from the title and length fields from the Tracks table

There are other keywords that you can use with SELECT. Run the following to see what they do.

Run the following to see what COUNT and LIMIT do.

SELECT bike_number, duration FROM trip_data LIMIT 5; SELECT COUNT(bike_number) FROM trip_data;

Run the following to see what MAX does

SELECT bike_number FROM trip_data LIMIT 10; SELECT MAX(bike_number) FROM trip_data;

Run the following to see what ORDER BY does

SELECT * FROM trip_data ORDER BY bike_number LIMIT 20

Run the following to see what ORDER BY does

SELECT * FROM trip_data ORDER BY bike_number DESC LIMIT 15

Q-6: Match each SQL option to what it does Check above to see what each command does.
• LIMIT n
• Limits the number of items returns to n.
• Count(field)
• Returns the number of items in the specified field (column).
• Max(field)
• Returns the maximum value in a field (column).
• ORDER BY field
• Returns the data sorted in ascending order by the specified field.
• ORDER BY field DESC
• Returns the data sorted in descending order by the specified field.

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Given a database of bike share information write a SELECT statement to retrieve the bike_number and duration from table trip_data but order the data by bike_number in descending order and limit the number of items returned to 5.

==== assert 0,0 == w01117 assert 0,1 == 225 assert 1,0 == w01117 assert 1,1 == 626 assert 2,0 == w01117 assert 2,1 == 288 assert 3,0 == w01117 assert 3,1 == 559 assert 4,0 == w01117 assert 4,1 == 980

What happens if you try to limit the number of items returned before you specify how to sort the data in the SQL above?

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