Grokking SQL for Tech Interviews
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4. Biggest Single Number

Problem

Table: MyNumbers

+-------------+------+
| Column Name | Type |
+-------------+------+
| num         | int  |
+-------------+------+
This table may contain duplicates (In other words, there is no primary key for this table in SQL).
Each row of this table contains an integer.

Problem Definition

A single number is a number that appeared only once in the MyNumbers table.

Find the largest single number. If there is no single number, report null.

Example

Output

Try It YourSelf

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Christopher Guy Slater

Christopher Guy Slater

· 9 days ago

-- another way
SELECT 
  num
FROM MyNumbers
GROUP BY num 
HAVING COUNT(*) = 1 
ORDER BY num DESC
LIMIT 1;
Sourav Singh

Sourav Singh

· 2 months ago

-- TODO: Write your user queries here
SELECT MAX(single_number) AS num
FROM (
  SELECT num as single_number
  FROM MyNumbers
  GROUP BY num
  HAVING COUNT(num) = 1
) AS filtertable;

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