sql - MySQL how to group into subgroups of rows -


i have db: (note id unique)

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i trying this:

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what efficient sql query achieve this?

select      distinct     foo2.group_id group_id,     if(foo1.group_id = foo2.group_id, foo1.id, null) id,     if(foo1.group_id = foo2.group_id, foo1.some_attr, null) some_attr  mytable foo1     join     (select distinct group_id mytable) foo2             order group_id, id

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