二、表操作
三、資料操作
四、日期時間處理
create
database mydb;
show
databases
;
drop
database mydb;
use mydb;select
database()
;
show
tables
;
create
table
user
( id int(11
)not
null
comment
'序號'
, username varchar(50
)null
comment
'姓名'
, *** tinyint(4
)null
comment
'性別'
, age int(11
)null
comment
'年齡'
, education int(11
)null
comment
'學歷，列舉值..'
,primary
key(
`id`
)using
btree
);
desc
user
;
drop
table
user
;
truncate
table
user
;
delete
from
user
;
rename
table old_user to new_user;
rename
table
user
to old_user, user_bak to
user
;--多表間快速修改
alter
table
user
addcolumn id int(11
)not
null
;
alter
table
user
drop
column id;
alter
table
user
addindex index_name (username)
;
alter
table
user
drop
index index_name;
insert
into
user
(id, username, ***)
values(1
,'tom',1
);
delete
from
user
where id =
1;
update
user
set username =
'jay'
where id =
1;
select
*from
user
where id =
1;
select
distinct id from
user
;
# mysql沒有merge into方法
update
user u,
user_tmp ut
set u.username = ut.username
where
u.id = ut.id;
select
*from
user
order
by id;
select education from
user
group
by education;
# mysql沒有merge into方法
select
education,
group_concat( username order
by username )
from
user
group
by education;
select
now();
select
current_timestamp()
;
select date_format(
'2020-11-19 20:06:00'
,'%y-%m-%d %h:%i:%s');
--2020-11-19 20:06:00
select str_to_date(
'2020-11-19'
,'%y-%m-%d');
--2020-11-19
select str_to_date(
'2020-11-19 09:00:00'
,'%y-%m-%d %h:%i:%s');
--2020-11-19 09:00:00
select to_days(
'2020-01-01');
--737790
select time_to_sec(
'01:00:02');
--3602
select sec_to_time(
3602);
--'01:00:02'
select makedate(
2020,65
);--'2020-03-05'
select maketime(20,
25,30)
;--'20:25:30'
select unix_timestamp(
'2020-11-19 20:30:00');
-- 1605789000
select from_unixtime(
1605789000);
--'2020-11-19 20:30:00'
增加函式：date_add()
減少函式：date_sub()
select date_add(
'2020-11-19'
,interval
1year);
--2021-11-19
select date_sub(
'2020-11-19'
,interval
1month);
--2020-10-19
單位：second、minute、hour、day、month、year
select timestampdiff(
month
,'2020-09-01'
,'2021-09-01');
--12
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