mysql - SQL JOIN many-to-many -

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sorry minimalistic title don't know how describe in short. have 3 tables:

the table of groups

id | genre ----------------- 1  | action 2  | adventure 3  | drama

many many table

groupid | elementid -----------------     3   |    1     1   |    2     2   |    2     2   |    3     3   |    3

and table of elements

id | element ----------------- 1  | pride , prejudice 2  | alice in wonderland 3  | curious incident of dog in night time

all fine , simple. select trying achieve following

id | element                                         |  genre ------------------------------------------------------------- 1  | pride , prejudice                             | drama 2  | alice in wonderland                             | null 3  | curious incident of dog in night time     | drama

i want select all elements table elements , set genre field drama or null.

i'm trying in mysql.

thank in advance

it's possible little trick (outer join on many-to-many table, constraint groupid has 3 (for drama)

http://sqlfiddle.com/#!2/b7c18/2

select elements.id, elements.element, groups.genre   elements left outer join group_elements   on elements.id = group_elements.elementid  , group_elements.groupid = 3 left outer join groups   on group_elements.groupid = groups.id

left outer join means : take lines tables preceded (the ones on left hand side of left outer join, if will), if there's no lines corresponding them in following tables. condition on elements.id = group_elements.elementid , group_elements.groupid = 3 says if find matches our elementid, must drama (groupid = 3). left outer join on groups table, enables display genre column, or null if element not drama.


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