w3resource

SQL Exercise: Count the number available rooms

SQL hospital Database: Exercise-6 with Solution

6. From the following table, write a SQL query to count the number available rooms. Return count as "Number of available rooms".

Sample table: room


Sample Solution:

SELECT count(*) "Number of available rooms"
FROM room
WHERE unavailable='false';

Sample Output:

 Number of available rooms
---------------------------
                        29
(1 row)

Explanation:

The said query here in SQL that counts the number of available rooms in the room table.

The query selects all columns (*) from the room table where the unavailable column is set to 'false'.

The resulting output is a single row with a single column, showing the number of available rooms in the room table. The column will be labeled "Number of available rooms".

Pictorial presentation:

Count the number available rooms

Practice Online


E R Diagram of Hospital Database:

E R Diagram: SQL Hospital Database.

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous SQL Exercise: Find the floor and block with a given room number.
Next SQL Exercise: Count the number of unavailable rooms.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Follow us on Facebook and Twitter for latest update.

SQL: Tips of the Day

Grouped LIMIT in PostgreSQL: Show the first N rows for each group?

db=# SELECT * FROM xxx;
 id | section_id | name
----+------------+------
  1 |          1 | A
  2 |          1 | B
  3 |          1 | C
  4 |          1 | D
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
  8 |          2 | H
(8 rows)

I need the first 2 rows (ordered by name) for each section_id, i.e. a result similar to:

id | section_id | name
----+------------+------
  1 |          1 | A
  2 |          1 | B
  5 |          2 | E
  6 |          2 | F
  7 |          3 | G
(5 rows)

PostgreSQL v9.3 you can do a lateral join

select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer
join lateral (
    select * from t t_inner
    where t_inner.section_id = t_outer.section_id
    order by t_inner.name
    limit 2
) t_top on true
order by t_outer.section_id;

Database: PostgreSQL

Ref: https://bit.ly/3AfYwZI

 





We are closing our Disqus commenting system for some maintenanace issues. You may write to us at reach[at]yahoo[dot]com or visit us at Facebook