sql notes: hackerrank the pads

Problem

Generate the following two result sets:

1. Query an alphabetically ordered list of all names in OCCUPATIONS, immediately followed by the first letter of each profession as a parenthetical (i.e.: enclosed in parentheses). For example: AnActorName(A), ADoctorName(D), AProfessorName(P), and ASingerName(S).
2. Query the number of ocurrences of each occupation in OCCUPATIONS. Sort the occurrences in ascending order, and output them in the following format:

There are a total of [occupation_count] [occupation]s.

where [occupation_count] is the number of occurrences of an occupation in OCCUPATIONS and [occupation] is the lowercase occupation name. If more than one Occupation has the same [occupation_count], they should be ordered alphabetically.
Note: There will be at least two entries in the table for each type of occupation.

Input Format
The OCCUPATIONS table is described as follows:

Occupation will only contain one of the following values: Doctor, Professor, Singer or Actor.

Sample Input
An OCCUPATIONS table that contains the following records:

Sample Output

Ashely(P)
Christeen(P)
Jane(A)
Jenny(D)
Julia(A)
Ketty(P)
Maria(A)
Meera(S)
Priya(S)
Samantha(D)
There are a total of 2 doctors.
There are a total of 2 singers.
There are a total of 3 actors.
There are a total of 3 professors.

Explanation
The results of the first query are formatted to the problem description’s specifications.
The results of the second query are ascendingly ordered first by number of names corresponding to each profession (2 ≤ 2 ≤ 3 ≤ 3), and then alphabetically by profession (doctor ≤ singer, and actor ≤ professor).

Analysis

We can use CONCAT() function to solve this problem. The syntax is ‘CONCAT(str1, str2, …)’ and it returns the string that results from concatenating the arguments.
And we can use SUBSTR() or LEFT() function to get first letter of Occupation. Syntax of SUBSTR() I use here is ‘SUBSTR(str, pos, len)’ and it returns a substring len characters long from string str, starting at position pos. Syntax of LEFT() is ‘LEFT(str, len)’ and it returns the leftmost len characters from the string str, or NULL if any argument is NULL.
Additionally,

• from OCCUPATIONS table ==> FROM OCCUPATIONS
• alphabetically ordered list of names ==> ORDER BY Name
• occupation_count ==> COUNT(Occupation) … GROUP BY Occupation
• lowercase occupation name ==> LOWER(Occupation)
• sort occurrences in ascending order ==> ORDER BY COUNT(Occupation)
• order alphabetically if having the same occupation_count ==>
  ORDER BY COUNT(Occupation), Occupation

Solution

Solution 1

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SELECT CONCAT(Name, '(', SUBSTR(Occupation,1,1),')') FROM OCCUPATIONS ORDER BY Name;
SELECT CONCAT('There are a total of ', COUNT(Occupation), ' ', LOWER(Occupation), 's.') FROM OCCUPATIONS GROUP BY Occupation ORDER BY COUNT(Occupation), Occupation;

Solution 2

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SELECT CONCAT(Name, '(', LEFT(Occupation,1),')') FROM OCCUPATIONS ORDER BY Name;
SELECT CONCAT('There are a total of ', COUNT(Occupation), ' ', LOWER(Occupation), 's.') FROM OCCUPATIONS GROUP BY Occupation ORDER BY COUNT(Occupation), Occupation;

Link

The PADS
(中文版) SQL 笔记: Hackerrank The PADS