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MySQL ?? ??? ?? ??

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  2. ?? ??: ???? ?? ?? ???? ???? ?? ?? ??? ?? ??? ???? ?????.

?? ??? ?? ??? ?? ? ?? ????? ??? ???? ??????.

  1. ??? ??? ???? User ???
  2. ?? ???? ?? ??? ????? ???? Order ???

user ??? ???

???? ?? ?? ??? ?? user (user (
   uid int(11) NOT NULL,
   username varchar(30) NOT NULL,
   password char(32) NOT NULL
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS order_goods (
   oid int(11) NOT NULL,
   uid int(11) NOT NULL,
   name varchar(50) NOT NULL,
   buytime uid int(11) NOT NULL,
username varchar(30) NOT NULL,

password char(32) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

???? ?? ?? ??? ?? order_goods (oid int(11) NOT NULL,uid int(11) NOT NULL,?? varchar(50) NOT NULL, ) ENGINE=InnoDB DEFAULT CHARSET=utf8;uidusernamepassword1Jingtian 1 234562 ????2456673????12355314???1234555 ???5abcwa6 ????abcdeef 7anglebabycaption8TFBOYSabcdwww9An Xiao chao12tfdd wd10Gao Xiaofeng13????121rcfwr fq14????123123tcsd15 ????3cxvdfs

order_goods ???? ??? ????:

?? ?? int(11) NOT NULL??? ??? ???? ??? ????:
??
5?? order_goods ????? uid? ??? ???? uid ??? ?????. ? ??? oid? ?? ??? ?? 1?? uid? ?? ???? 10???. ??? ???? uid 10? ?? ???? ??: Gao Xiaofeng. ???? Apple ???? ??????. ?? ?? buytime? ??? ????????. ?? ??category??? ???? ??? 1? ?????. ?? [??], ? n? ? 1 [??]?? ??? ?????. ], ??? n ??? ??
oiduidnamebuytime
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23??? ?? 4242123
3??? ???12123413
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?? ?? 1:

?

user.uid,user.username? ??? ??,order_goods.oid,order_goods.uid,order_goods.name?? user,order_goods?? ??, ??? user.uid = order_goods.uid ;

?? ???? ????? ?? ???? ??? ????? ???? ??? ??? ?????

??: ?? ??? from ???? ??? ??? ?????.

??? ??? ?? ??? ??? ??? ???? ????. ??? ?? ???? ???? ?? ?? ??? ? ????. ??? ??? ??? ?? ?? string.field? ?????.

mysql> ??? u,order_goods o?? ??? ???? u.uid,u.username, o.oid,o.uid,o.name? ?????. ??? u.uid = o.uid;
+------+------------+------+------+---------------+
| ??? | ??? | +------+------------+------+------+---------------+
10 | ????? | 10 | 3 | ???? 2 | 12 | ????? 12 | 15 | 3 | ? ??? | 3 | +------+------------+------+------+---------------+
5? ??(0.00?)


?? ?? 2:


category

??? ??
??? 1. ?? [??], ??? n ?? ?? ? 1 ??? ?? INNER JOIN ??? n;
  • ?? ??
    Exampleuser.uid,user.username? ??? ???? ??,order_goods.oid,order_goods.uid,order_goods.name? ??? ?? ???? shopname?? user.uid? order_goods = order_goods.uid;
    ?? ???? ????? ?? ???? ??? ????? ???? ??? ??? ?????

    ??? ???? 1? ?????.

    mysql> ??? ?? ?? order_goods?? ??? ???? user.uid,user.username, order_goods.oid,order_goods.uid,order_goods.name? ?? ???? ?? = order_goods.uid;
    +------+------------+------+------+---------------+
    | ??? | ??? | +------+------------+------+------+---------------+
    10 | ????? | 10 | 3 | ???? 2 | 12 | ????? 12 | 15 | 3 | ???? 5 |
    +------+------------+------+------+---------------+
    5? ??(0.00?) ?? ?? JOIN ??? n on ??;



    Example

    select * from user left Join order_goods on user.uid = order_goods.uid;

    ?? ?? ?? on the ??, ??? ???? ?? ???? ???? ??? ??? ?????

    ?? ??? ?? ??? ??? ??? ???? ???? ??? ??? ????.

    ?? ??: ??? ???? ???? ???? ?? ???? ???? ?? ???? ?? ???? ?????.

    mysql> select * from user left Join order_goods on user.uid = order_goods.uid;
    +-- - --+------------+---+------+------+---- --- -------+----------+
    | ??? ?? | oid ?? |
    +----+- --- ----+------------+------+------+------------- --+ -----------+
    | 10 | ?? ??? | 1235531 | 3121241 |
    | 12 | 3cxvdfs | 1235531 |5 |??? ??? 123456 | NULL | NULL | NULL | |
    | 5abcwa | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | | NULL | NULL ----------+------+------+---------------+---- ---- --+
    16? ??(0.00?)

    ??? ??: ??? ???? ???? ?? ???? ???? ??? ???? ?? ???? ?????

    Category??? ??
    ?? ??? 1? ?????. ?? [????], ??? n. ??? 1? ?? ??? JOIN ??? n ??;
    Exampleselect * from user right Join order_goods on user.uid = order_goods.uid;
    ?? ?? ?? ???? ?? ???? ??? ????? ???? ??? ??? ?????

    mysql> ??? ???? *? ???? user.uid?? order_goods? ?? = order_goods.uid;
    +------+- - ---------+------------+------+------+---------------+ - ----------+
    | ??? ?? | oid | ?? ?? |
    +-------+- ------+------+------+---------------+------------+
    | 10 | 3124qwqw | ?? ??? | 1235531 | 12 | 3 | 12 | 15 | 3cxvdfs | 3424212 | 121234 13 | --- ------+------------+------+------+---------------+---- -- ----+
    5? ?(0.00?)

    Subquery

    ??? ??? ? ??? ??? ?? select ?? ??? ?? ?? ??? ???? ???. ?? ??? ???? ????? in, not in, =, !=, ???, ???? ?? ?? ?????.

    Category

    ??? ???? ??select field from table where field in (condition)? 1select * from user where uid in (1, 3 , 4);?? 1 ??ID? ??? ??? ???? 2select * from user where uid in(order_goods?? uid ??);?? 2 ?? ?? ??? ??? ??? ??? ?????

    ? 1:

    mysql> uid? (1,3,4);
    ? ????? *? ?????. +------+------------+----------+
    | ??? ?? |
    +------+------------+----------+
    1 | ??? | 3 |???? | 4 | ??? 123455 |
    +------+------------+----------+
    3? ??(0.00?)

    ? 2:

    mysql> select * from user where uid in(order_goods?? uid ??);
    +------+------------+----------+

    | ??? ?? |
    +------+------------+----------+
    10 | ????? | 3 |???? | 12 | ? ???? |
    15 | ???? | +------+------------+----------+
    4 ? ??(0.00?)


    mysql> select * from emp where deptno in(dept?? deptno ??);

    Union ??

    Union ? Union All ???? ???? ? ???? ???? ?????. a ?? ?? ??? ??? ? ??? ???? ?? ?????. ?? ?? ???? ??? ?? ????? ???, ???? ?? ?? ? ??? ?? ??? ??? ???? ??? ???? ??? ?????.

    Category

    ??? ???? ??select ? 1 Union[all] select ? 2Exampleselect * from user where uid in (1, 3, 4 );?? ??? ???? ??? ??? ??? ???? ??? ??? ?????mysql> ??? ???? uid ?? order_goods?? uid ??; +------+ |
    +------+
    1 |

    2 |
    3 |
    4 |
    5 |
    6 |
    7 |
    8 |
    9 |
    10 |
    11 |
    12 |
    13 |
    14 |
    15 |
    +------+
    15? ?? (0.00?)


    ???? ??

    ||
    <?php echo "Hello Mysql"; ?>
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