SQL Exercise: Count the number of unavailable rooms

SQL hospital Database: Exercise-7 with Solution

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

Sample table: room

Sample Solution:

-- This SQL query counts the number of unavailable rooms from the room table where the 'unavailable' column is set to 'true'.

SELECT count(*) "Number of unavailable rooms" -- Counts the number of rows and aliases the result column as "Number of unavailable rooms"
FROM room -- Specifies the table from which to retrieve data, in this case, the room table
WHERE unavailable='true'; -- Filters the rows to include only those where the 'unavailable' column is set to 'true'

Sample Output:

Number of unavailable rooms
---------------------------
                         7
(1 row)

Explanation:

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

The query selects all columns (*) from the room table where the unavailable column is set to 'true'. The resulting output will be a single row with a single column, showing the number of unavailable rooms in the room table. The column will be labeled "Number of unavailable rooms".

Pictorial presentation:

Practice Online

E R Diagram of Hospital Database:

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