How to Select Distinct Values Across Multiple Columns in MySQL?

Selecting Distinct Values Across Multiple Columns in MySQL

Selecting unique or distinct values from a database is a crucial aspect of data management. This can be achieved using the DISTINCT keyword in conjunction with the appropriate columns. However, when dealing with multiple columns, it's common to encounter duplicate entries due to different ordering of the values.

In the example provided, a table with two columns, foo and bar, demonstrates the issue. A query using SELECT DISTINCT foo, bar from table yields the following result:

foo bar
a   c
c   f
d   a
c   a
f   c

As you can see, while the values are distinct within each column, they repeat when combined. To address this, we can leverage the GROUP BY clause. By grouping the results based on both foo and bar, we force MySQL to consider only distinct combinations of both columns:

SELECT foo, bar
FROM my_table
GROUP BY foo, bar

This query will produce the desired output:

foo bar
a   c
c   f
d   a

Using GROUP BY ensures that only distinct values from both columns are returned, providing a concise and accurate representation of the data.

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