Question

My friend asked this question to me –

You are given a table with just one field which is an integer. Can
you get the highest value in the field without using the MAX function
?

I think we can change the sign of each column and find the minimum using MIN function. Is that correct?

Answer 1

Why you would ignore using the function supported on any database is anyone’s guess, especially if you’d use the MIN function, but…

GREATEST

…some database vendors support the GREATEST function:

SELECT GREATEST(column)
  FROM ...

GREATEST returns the highest value, of all the columns specified. Those that support GREATEST include:

• MySQL
• Oracle
• PostgreSQL

TOP/LIMIT

TOP is SQL Server (2000+) only:

  SELECT TOP 1 column
    FROM YOUR_TABLE
ORDER BY column DESC

LIMIT is only supported by MySQL, PostgreSQL and SQLite

  SELECT column
    FROM YOUR_TABLE
ORDER BY column DESC
   LIMIT 1

ROW_NUMBER

ROW_NUMBER is supported by PostgreSQL 8.4+, Oracle 9i+, SQL Server 2005+:

SELECT x.col
  FROM (SELECT column AS col, 
               ROW_NUMBER() OVER (ORDER BY column DESC) AS rank
          FROM YOUR_TABLE) x
 WHERE x.rank = 1