MySQL； GROUP BY 但仅当列不为空时

Question

I have the following SQL query:

SELECT * FROM my_table GROUP BY B,D,F;

If there are some rows where B is empty and D is empty AND F is empty, it'll grouped to a single row where all the three columns are empty.

But instead I want: in case all three columns (B, D, F) of a row are empty don't group this row show it.

Means: If I have the following:

result should be:

How can I do this?

Answer 1

Firstly, you are selecting * with group by !! not sure if this is going to work with you.

Anyway, to achieve what you want try this

SELECT B,D,F
FROM your_table
WHERE NOT (B='' AND D='' AND F='')
GROUP BY B,D,F

UNION ALL

SELECT B,D,F
FROM your_table
WHERE B='' AND D='' AND F=''

Answer 2

try

SELECT * FROM my_table GROUP BY B,D,F,IF((B="" AND D="" AND F=""),id,0);

assuming that id is a unique key.

if any of the columns you want to group by aren't empty, zero is retuned instead of id, but if all three ARE empty, then id is returned, and thus ones with all three others empty are no longer grouped.

And yes, this works with select *.