MySQL學習筆記 子查詢

子查詢是將乙個查詢語句巢狀在另乙個查詢語句中。內層查詢語句的查詢結果，可以作為外層查詢語句提供條件。

insert

[into
] tbl_name [
(col_name,..
.)]select..
.

create

table[if
notexists
] tbl_name
[(create_definition,..
.)]select_statement

-- 由[not] in引發的子查詢

select username,depid from employee where depid in
(select id from department)
;select username,depid from employee where depid notin(
select id from department)
;-- 建立學員表student
-- id username score
create
table
ifnot
exists student
(    id       tinyint
unsigned
auto_increment
key,
username varchar(20
)not
null
unique
,    score    tinyint
unsigned);
insert student(username, score)
values
('king',95
),('king1',35
),('king2',45
),('king3',55
),('king4',65
),('king5',75
),('king6',80
),('king7',90
),('king8',25
);-- 建立獎學金scholarship
-- id ,level
create
table
ifnot
exists scholarship
(    id    tinyint
unsigned
auto_increment
key,
level
tinyint
unsigned);
insert scholarship(
level
)values(90
),(80
),(70
);select
*from scholarship;
select
*from student;
-- 查詢獲得1等獎學金的學員有
select username
from student
where score >=
(select
level
from scholarship where scholarship.id =1)
;-- 查詢部門表中
select
*from department
where id =4;
select id, username
from employee
where
exists
(select
*from department where id =3)
;-- 查詢所有獲得獎學金的學員
select id, username, score
from student
where score >=
any(
select
level
from scholarship)
;select id, username, score
from student
where score >=
some
(select
level
from scholarship)
;-- 查詢所有學員中獲得一等獎學金的學員
select id, username, score
from student
where score >=
all(
select
level
from scholarship)
;-- 查詢學員表中沒有獲得獎學金的學員
select id, username, score
from student
where score <
all(
select
level
from scholarship)
;select id, username, score
from student
where score <
any(
select
level
from scholarship)
;select id, username, score
from student
where score <=
any(
select
level
from scholarship)
;-- 相當於in
select id, username, score
from student
where score =
any(
select
level
from scholarship)
;select id, username, score
from student
where score in
(select
level
from scholarship)
;-- 相當於not in
select id, username, score
from student
where score notin(
select
level
from scholarship)
;select id, username, score
from student
where score <>
all(
select
level
from scholarship)
;

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