MySQL select one column DISTINCT, with corresponding other columns

Question

try this query

 SELECT ID, FirstName, LastName FROM table GROUP BY(FirstName)

To avoid potentially unexpected results when using GROUP BY without an aggregate function, as is used in the accepted answer, because MySQL is free to retrieve ANY value within the data set being grouped when not using an aggregate function [sic] and issues with ONLY_FULL_GROUP_BY. Please consider using an exclusion join.

Exclusion Join - Unambiguous Entities

Assuming the firstname and lastname are uniquely indexed (unambiguous), an alternative to GROUP BY is to sort using a LEFT JOIN to filter the result set, otherwise known as an exclusion JOIN.

See Demonstration

Ascending order (A-Z)

To retrieve the distinct firstname ordered by lastname from A-Z

Query

SELECT t1.*
FROM table_name AS t1
LEFT JOIN table_name AS t2
ON t1.firstname = t2.firstname
AND t1.lastname > t2.lastname
WHERE t2.id IS NULL;

Result

| id | firstname | lastname |
|----|-----------|----------|
|  2 |      Bugs |    Bunny |
|  1 |      John |      Doe |

Descending order (Z-A)

To retrieve the distinct firstname ordered by lastname from Z-A

Query

SELECT t1.*
FROM table_name AS t1
LEFT JOIN table_name AS t2
ON t1.firstname = t2.firstname
AND t1.lastname < t2.lastname
WHERE t2.id IS NULL;

Result

| id | firstname | lastname |
|----|-----------|----------|
|  2 |      Bugs |    Bunny |
|  3 |      John |  Johnson |

You can then order the resulting data as desired.

---

Exclusion Join - Ambiguous Entities

If the first and last name combination are not unique (ambiguous) and you have multiple rows of the same values, you can filter the result set by including an OR condition on the JOIN criteria to also filter by id.

See Demonstration

table_name data

(1, 'John', 'Doe'),
(2, 'Bugs', 'Bunny'),
(3, 'John', 'Johnson'),
(4, 'John', 'Doe'),
(5, 'John', 'Johnson')

Query

SELECT t1.*
FROM table_name AS t1
LEFT JOIN table_name AS t2
ON t1.firstname = t2.firstname
AND (t1.lastname > t2.lastname
OR (t1.firstname = t1.firstname AND t1.lastname = t2.lastname AND t1.id > t2.id))
WHERE t2.id IS NULL;

Result

| id | firstname | lastname |
|----|-----------|----------|
|  1 |      John |      Doe |
|  2 |      Bugs |    Bunny |

---

Composite IN() Subquery - Unambiguous Entities

For larger datasets, using an exclusion join can be very slow. If you have unambiguous entries, an alternative is to use a Composite IN() criteria against a MIN/MAX aggregate subquery.

Demonstration

Ascending Order (A-Z)

Query

SELECT t1.*
FROM table_name AS t1
WHERE (t1.firstname, t1.lastname) IN(
   SELECT firstname, MIN(lastname)
   FROM table_name
   GROUP BY firstname
)

Result

| id | firstname | lastname |
|----|-----------|----------|
|  2 |      Bugs |    Bunny |
|  1 |      John |      Doe |

Descending Order (Z-A)

Query

SELECT t1.*
FROM table_name AS t1
WHERE (t1.firstname, t1.lastname) IN(
   SELECT firstname, MAX(lastname)
   FROM table_name
   GROUP BY firstname
)

Result

| id | firstname | lastname |
|----|-----------|----------|
|  2 |      Bugs |    Bunny |
|  3 |      John |  Johnson |

---

Composite IN() Dependent Subquery - Ambiguous Entities

The same theory can be applied from the Ambiguous Exclusion join to the composite IN() subquery method, by adding a dependent subquery with MIN/MAX on the id column.

Demonstration

Query

SELECT t1.*
FROM table_name AS t1
WHERE t1.id IN(
   SELECT MIN(id)
   FROM table_name
   WHERE (t1.firstname, t1.lastname) IN(
      SELECT firstname, MIN(lastname)
      FROM table_name
      GROUP BY firstname
   )
   GROUP BY firstname, lastname
);

Result

| id | firstname | lastname |
|----|-----------|----------|
|  1 |      John |      Doe |
|  2 |      Bugs |    Bunny |

---

Ordered Subquery

EDIT

My original answer using an ordered subquery, was written prior to MySQL 5.7.5, which is no longer applicable, due to the changes with ONLY_FULL_GROUP_BY. Please use the one of the examples above instead.

It is also important to note; when ONLY_FULL_GROUP_BY is disabled (original behavior prior to MySQL 5.7.5), the use of GROUP BY without an aggregate function may yield unexpected results, because MySQL is free to choose ANY value within the data set being grouped [sic].

Meaning an ID or lastname value may be retrieved that is not associated with the retrieved firstname row.

---

WARNING

With MySQL GROUP BY may not yield the expected results when used with ORDER BY

See Test Case Example

The best method of implementation, to ensure expected results, is to filter the result set scope using an ordered subquery.

table_name data

(1, 'John', 'Doe'),
(2, 'Bugs', 'Bunny'),
(3, 'John', 'Johnson')

Query

SELECT * FROM (
    SELECT * FROM table_name ORDER BY ID DESC
) AS t1
GROUP BY FirstName

Result (MySQL 5.6)

| ID | first |    last |
|----|-------|---------|
|  2 |  Bugs |   Bunny |
|  3 |  John | Johnson |

---

Comparison

To demonstrate the unexpected results when using GROUP BY in combination with ORDER BY

Query

SELECT * FROM table_name GROUP BY FirstName ORDER BY ID DESC

Result (MySQL 5.6)

| ID | first |  last |
|----|-------|-------|
|  2 |  Bugs | Bunny |
|  1 |  John |   Doe |

The DISTINCT keyword doesn't really work the way you're expecting it to. When you use SELECT DISTINCT col1, col2, col3 you are in fact selecting all unique {col1, col2, col3} tuples.

SELECT ID,LastName 
From TABLE_NAME 
GROUP BY FirstName 
HAVING COUNT(*) >=1

How about

`SELECT 
    my_distinct_column,
    max(col1),
    max(col2),
    max(col3)
    ...
 FROM
    my_table 
 GROUP BY 
    my_distinct_column`

SELECT firstName, ID, LastName from tableName GROUP BY firstName

As pointed out by fyrye, the accepted answer pertains to older versions of MySQL in which ONLY_FULL_GROUP_BY had not yet been introduced. With MySQL 8.0.17 (used in this example), unless you disable ONLY_FULL_GROUP_BY you would get the following error message:

mysql> SELECT id, firstName, lastName FROM table_name GROUP BY firstName;

ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'mydatabase.table_name.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

One way to work around this not mentioned by fyrye, but described in https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html, is to apply the ANY_VALUE() function to the columns which are not in the GROUP BY clause (id and lastName in this example):

mysql> SELECT ANY_VALUE(id) as id, firstName, ANY_VALUE(lastName) as lastName FROM table_name GROUP BY firstName;
+----+-----------+----------+
| id | firstName | lastName |
+----+-----------+----------+
|  1 | John      | Doe      |
|  2 | Bugs      | Bunny    |
+----+-----------+----------+
2 rows in set (0.01 sec)

As written in the aforementioned docs,

In this case, MySQL ignores the nondeterminism of address values within each name group and accepts the query. This may be useful if you simply do not care which value of a nonaggregated column is chosen for each group. ANY_VALUE() is not an aggregate function, unlike functions such as SUM() or COUNT(). It simply acts to suppress the test for nondeterminism.