Mysql – Grouping and getting the Max(col1) row variables

greatest-n-per-groupMySQL

I have this table:

CREATE TABLE `table1` (
    `id` INT(11) NOT NULL AUTO_INCREMENT,
    `col1` VARCHAR(30) NULL DEFAULT NULL,
    `col2` VARCHAR(30) NULL DEFAULT NULL,
    `col3` VARCHAR(30) NULL DEFAULT NULL,
    `riskLevel` VARCHAR(30) NULL DEFAULT NULL
    PRIMARY KEY (`id`)
)COLLATE='utf8_general_ci' ENGINE=InnoDB;

What i want to do is group this table by col1, and get the row with the highest riskLevel for each col1 group values.

When using this query:

SELECT id,col1,col2,col3, MAX(riskLevel) 
FROM table1
GROUP BY col1

You get the max riskLevel, but the other values are random, not fittings to the correct row.

I know one solution:

SELECT id,col1,col2,col3, riskLvel
FROM table1 JOIN
(SELECT col1, MAX(riskLevel) as riskLevel
FROM table1
GROUP BY col1) x ON x.col1 = table1.col1 AND x.riskLevel = table1.riskLevel

This solution doesn't seem optimal to me.

Is there another way of getting the described behavior?

Best Answer

SELECT id,col1,col2,col3, riskLvel
FROM table1
where risklevel IN ( SELECT MAX(riskLevel)
                     FROM table1
                     GROUP BY col1 )

IF This query is not correct then you can try this query

SELECT id,col1,col2,col3, riskLvel
    FROM table1
    where col1 IN ( SELECT MAX(col1)
                         FROM table1
                         GROUP BY col1 )
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