sql - MySQL: Return all rows with same ID but filter by a different field -

in application, have table identifies resources (i.e. pictures) id. said resources have been "tagged" (field1). i.e. picture 3 in table below tagged both 'a' , 'b'. whereas picture 1 tagged 'a' , picture 2 tagged 'b'.

here "tagging" table:

+--------------+ |  id | field1 | +--------------+ |   1 |      | |   2 |      b | |   3 |      | |   3 |      b | +--------------+ 

note: id's neither unique nor auto-incrementing.

problem: want return pictures tagged 'b', not want return tagged 'a'.

select id pictures field1 = 'b';

returns:

+-----+ |  id | +-----+ |   2 | |   3 | +-----+ 

this not want want, because includes picture 3 tagged 'a' (in row preceding [3, b] in original table)

i want:

+-----+ |  id | +-----+ |   2 | +-----+ 

here 2 methods:

exists subclause:

select id  pictures pictures1 field1 = 'b'  , not exists (       select *       pictures picutures2       pictures2.id = pictures1.id      , pictures2.field1 = 'a'); 

left join:

select pictures1.id  pictures pictures1 left join pictures picutures2 on      pictures2.id = pictures1.id      , pictures2.field1 = 'a'  pictures1.field1 = 'b' , pictures2.id null -- line eliminates records join fails; note if have line, must not put other pictures2 references in clause 

;