How to Find the Maximum Value Across Multiple Columns in a Single SQL Row?

Find the maximum value of multiple columns in SQL

In SQL, it is often necessary to determine the maximum value of multiple columns in a single row. This can be achieved by using specialized functions and techniques.

A common approach is to use an aggregate function, such as MAX(), which calculates the maximum value of a specified set of values. By applying MAX() to multiple columns in the same row, you can get the maximum value for each column.

For example, consider the following data structure:

<code>TableName
---------------------------------------
| Number | Date1  | Date2  | Date3  | Cost  |
---------------------------------------
| 1      | 2023-01-01 | 2023-02-01 | 2023-03-01 | 100   |
| 2      | 2023-01-15 | 2023-02-15 | 2023-03-15 | 150   |
| 3      | 2023-02-05 | 2023-03-05 | 2023-04-05 | 200   |</code>

To return the maximum date and cost for each row, you can use the following query:

SELECT Number,
       GREATEST(Date1, Date2, Date3) AS Most_Recent_Date,
       MAX(Cost) AS Max_Cost
FROM TableName;

This query uses the GREATEST() function to calculate the maximum value of the date column for each row, and the MAX() function to calculate the maximum value of the cost column. No GROUP BY clause is needed because we calculate the maximum value for each row.

The query results are as follows:

<code>Number | Most_Recent_Date | Max_Cost
-----------------------------------------
1      | 2023-03-01      | 100
2      | 2023-03-15      | 150
3      | 2023-04-05      | 200</code>

This technique provides a convenient way to extract the maximum value of multiple columns in SQL. It works for any data structure where you need to find the maximum value of a specific column. It should be noted that the GREATEST() function is not supported by all SQL databases, and some databases may need to use other equivalent functions or CASE statements to achieve the same functionality.

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