mysql - Do Multiple Left Join on condition and get non null column value -

i have table containing last comments posted on website, , i'd join different table depending on comment type.

comments table similar structure:

id | type | ressource_id | ---+------+--------------+ 1  |  1   |      10      | 2  |  3   |       7      | 3  |  3   |      12      | 4  |  1   |      22      | 5  |  4   |      22      | 6  |  5   |      23      | 

news table:

news_id | notes|     date     | --------+------+--------------+ 10      |      |  2015-08-12  | 22      |      |  2015-07-12  | 

tutorial table:

tuto_id | notes|     date     | --------+------+--------------+ 7       |      |  2015-06-15  | 12      |      |  2015-05-14  | 

... similar table type = 4, 5, 6

now in order specific comments doing left join on 2 tables.

select co.*   comments co        left join news n                on co.id = n.news_id , co.type = 1        left join tutorial t               on co.id = t.tuto_id , co.type = 3  (co.type in (1,3))  

i interested in getting date left table. how can include column in output list.

result desired: (date joining table)

id | type | ressource_id |     date     | ---+------+--------------+--------------+ 1  |  1   |      10      |  2015-08-12  | 2  |  3   |       7      |  2015-06-15  | 3  |  3   |      12      |  2015-05-14  | 4  |  1   |      22      |  2015-07-12  | 

thanks.

since never date news , tutorial same comment might go withcoalesce`:

select co.*, coalesce(n.date,t.date)   comments co        left join news n                on co.id = n.news_id , co.type = 1        left join tutorial t               on co.id = t.tuto_id , co.type = 3  (co.type in (1,3)) 

coalesce return first argument not null, if there matching news return date news , if there no matching news matching tutorial return date tutorial.