create table join_teacher(
id int primary key auto_increment,
t_name varchar(10) not null,
gender enum('male','female','secret') not null
)engine innodb character set utf8;
insert into join_teacher values
(1,'韓信','male'),
(2,'李白','male'),
(3,'韓非子','secret');
create table join_class(
id int primary key auto_increment,
c_name varchar(10) not null,
root int not nclass values
(1,'php0115',207),
(2,'php0115',207),
(3,'php0115',207);
create table join_day(
id int primary key auto_increment,
t_id int not null,
c_id int not null,
days tinyint not null,
begin_date date not null,
end_date date not null
)engine innodb character set utf8;
insert into join_day values
(1,1,1,15,20130115,20130220),
(2,2,2,20,20130222,20130325),
(3,3,3,15,20130327,20130418);
tbl_left inner join tbl_right on 連線條件
inner join
select join_teacher.t_name,join_teacher.gender,join_day.begin_date,join_day.end_date
from join_teacher inner join join_day on
join_teacher.id=join_day.t_id;
select * from join_teacherinner joinjoin_day on
join_teacher.id=join_day.t_id;
leftouter join
select * from join_teacher left outer join join_day on
join_teacher.id=join_day.t_id;
join 連線查詢：將多個表的記錄連線起來
分類：內連線，外連線，自然連線
內連線：資料內部的連線，要求：連線的多個資料必須存在才能連線
外連線：如果負責連線的乙個或多個資料不真實存在，則稱之為外連線
select s.*,si.* from info_class as cleft joininfo_student as s on c.id=s.class_id
left joininfo_student_info as si on s.id=si.id where c.class_name='php0331';
select child.* from hd_cate as parent left join hd_cate as child on child.pid=parent.id where parent.name='mysql';
格式：select * from table1
left join table2 on 條件
left join table3 on 條件
......
按列往後加資訊ull
)engine innodb character set utf8;
insert into join_
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資料庫 連線（自然連線 外連線 內連線）
1 自然連線 只考慮那些在兩個關係模式中都出現的屬性上取值相同的元組對natural join join.using select a1,a2,an from r1 natural join r2 natural join natural join rn where p select name1,c...
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