MySQL學習筆記（一） 各種連線表的方法

inner join (內連線)

outer join (外連線)

cross join

natural join

顯式:

use

database
;select
*from table_1 t1
join table_2 t2 on t1.id = t2.id;

use

database
;select
*from table_1 t1, table_2 t2
where t1.id = t2.id;

use

database
;select
*from table_1 t1
join table_2 t2 on t1.id = t2.id and t1.product_id = t2.product_id;

use

database
;select
*from table_1 t1
join table_2 t2 using
(id)
;

use sql_store;

select 
order_id,
order_date,
'active'
asstatus
from orders
where order_date >=
'2019-01-01'
union
select 
order_id,
order_date,
'archived'
asstatus
from orders
where order_date <
'2019-01-01'
;

use

database
;select
*from table_1 t1
join table_2 t2 on t1.id = t2.id;

use sql_hr;

select
*from employees e
join employees m on e.reports_to = m.employee_id;

use database_1;

select
*from table_1 t1
join database_2.table_2 t2 on t1.id = t2.id;

use

database
;select
*from table_1 t1
join table_2 t2 on t1.id = t2.id
join table_3 t3 on t2.id = t3.id;

use

database
;select
*from table_1 t1
left
join table_2 t2 on t1.id = t2.id;

use

database
;select
*from table_1 t1
right
join table_2 t2 on t1.id = t2.id;

use sql_hr;

select
*from employees e
left
join employees m on e.reports_to = m.employee_id;

use

database
;select
*from table_1 t1
cross
join table_2 t2 on t1.id = t2.id
order
by t1.name;

use

database
;select
*from table_1 t1
natural
join table_2 t2;

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