mysql - Why are variables being cut out? -

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high school students trying create version of facebook our school. right stuck on joining tables in trial database before can release it.

to join tables post, users, , friends:

users user    name 1       hallie   2       dylan 3       sarina 4       dominic  friends user    friend 1       2 1       3 1       4 2       1 3       1 4       1 2       4 4       2 3       2 2       3  posts | user | postid | post | +------+--------+------+ |    1 |    101 |  tigerbook!          | |    2 |    102 |  pregnant.              | |    1 |    103 |  peeps                | |    4 |    104 |  giant buzz lightyears rock. | |    3 |    105 |  die tucker die              | |    1 |    106 |  murhur de derpity derp      | |    2 |    107 |  banana spaghetti squid      | |    4 |    108 |  chicken                     |

we used code:

select users.user,         users.name,         posts.postid,         posts.post,         tmp.friend    (select friend,                 user            friends          group  friend) tmp         join users           on tmp.user = users.user         join posts           on posts.user = users.user;

and comes result of:

+------+---------+--------+-------------------------+--------+ | user | name    | postid | post                    | friend | +------+---------+--------+-------------------------+--------+ |    1 |  hallie |    101 |  tigerbook!     |      2 | |    1 |  hallie |    101 |  tigerbook!     |      3 | |    1 |  hallie |    101 |  tigerbook!     |      4 | |    2 |  dylan  |    102 |  pregnant.         |      1 | |    1 |  hallie |    103 |  peeps           |      2 | |    1 |  hallie |    103 |  peeps           |      3 | |    1 |  hallie |    103 |  peeps           |      4 | |    1 |  hallie |    106 |  murhur de derpity derp |      2 | |    1 |  hallie |    106 |  murhur de derpity derp |      3 | |    1 |  hallie |    106 |  murhur de derpity derp |      4 | |    2 |  dylan  |    107 |  banana spaghetti squid |      1 | +------+---------+--------+-------------------------+--------+

it cuts out posts 104, 105, , 108. posted users 3 , 4. , ignores fact user 2 friends 3 , 4, 1 shows.

why not bringing users 3 , 4? should try different code?

look subquery returns:

| friend | user | ----------------- |      1 |    2 | |      2 |    1 | |      3 |    1 | |      4 |    1 |

because of group by, lose multiple user values associated friends.

why did use subquery instead of joining friends table itself?

select users.user,    users.name,    posts.postid,    posts.post,    friends.friend friends    join users      on friends.user = users.user    join posts      on posts.user = users.user; 
| user |    name | postid |                        post | friend | ------------------------------------------------------------------ |    1 |  hallie |    101 |          tigerbook! |      2 | |    1 |  hallie |    103 |                peeps |      2 | |    1 |  hallie |    106 |      murhur de derpity derp |      2 | |    1 |  hallie |    101 |          tigerbook! |      3 | |    1 |  hallie |    103 |                peeps |      3 | |    1 |  hallie |    106 |      murhur de derpity derp |      3 | |    1 |  hallie |    101 |          tigerbook! |      4 | |    1 |  hallie |    103 |                peeps |      4 | |    1 |  hallie |    106 |      murhur de derpity derp |      4 | |    2 |   dylan |    102 |              pregnant. |      1 | |    2 |   dylan |    107 |      banana spaghetti squid |      1 | |    2 |   dylan |    102 |              pregnant. |      3 | |    2 |   dylan |    107 |      banana spaghetti squid |      3 | |    2 |   dylan |    102 |              pregnant. |      4 | |    2 |   dylan |    107 |      banana spaghetti squid |      4 | |    3 |  sarina |    105 |              die tucker die |      1 | |    3 |  sarina |    105 |              die tucker die |      2 | |    4 | dominic |    104 | giant buzz lightyears rock. |      1 | |    4 | dominic |    108 |                     chicken |      1 | |    4 | dominic |    104 | giant buzz lightyears rock. |      2 | |    4 | dominic |    108 |                     chicken |      2 |

http://sqlfiddle.com/#!2/27eb3d/6


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