mysql - Overcoming Extra Rows -

i have insert multiple columns different tables keep having same problem.

the problem this: can insert column tablea.columna tableb.columna no problem. next need insert tablec.columna tableb.columnb , insert command adds rows change id's of data.

my insert commands, plus update command executing id's match (unsuccessfully) below.

i know insert command can add rows how passed id's match?

i thought maybe columns had auto increment set not -- not seem problem. appreciated.

(1) insert users_posts             (author_id,              post_id,              post_title)       select contents.user_id, contents.id, contents.title      contents      contents.id = id  (2) insert users_posts             (post_content)       select content_bodies.content      content_bodies      content_bodies.id = id  (3) update users_posts      set post_content  = (select content_bodies.content                            content_bodies                            content_bodies.id = users_posts.post_id) 

if understand question correct, not want second , third statements, rather update statement update users_posts.post_content

if insert (assuming doesn't fail other reasons i.e. constraints) insert new rows, hence keyword insert.

try statement adds post content users_posts table content_bodies table based on ids!

update users_posts u  join content_bodies b  on b.id = u.post_id  set u.post_content = b.content; 

see in action sqlfiddle

edit

please run query , let me know if matches data correctly

select * users_posts u join content_bodies b  on b.id = u.post_id