mysql中的一些稍微复杂用法实例代码

mysql的语法相信对大家来说都不是难事，但是本文主要给分享了一些mysql复杂用法的相关内容，通过这篇文章相信大家会对mysql更深的了解一些，下面话不多说了，来一起看看详细的介绍吧

一对多数据显示成一行

GROUP_CONCAT(expr)

1、涉及的表关系:teacher表、teacher_subject_rel表(教师所能教的学科表)、subject表

2、业务场景:

需要拉取所有教师的编号(teacher_no)、学科名(subject_name)。

&nbsp

教师表(teacher)和学科(teacher_subject_rel)是一对多关系,

往往查询出现的是同一教师多条

数据。我们希望得到每个教师一条数据

学科拼接成一条

1、基本语法

group_concat(

[DISTINCT]

要连接的字段

[Order

BY

排序字段

ASC/DESC]

[Separator

'分隔符']

)

2、例子

SELECT

t.teacher_id

as

'教师id',

t.teacher_no

'教师编号',

(

SELECT

GROUP_CONCAT(s.subject_name)

FROM

teacher_subject_rel

tsr

LEFT

JOIN

`subject`

s

ON

tsr.subject_id

=

s.subject_id

WHERE

t.teacher_id

=

tsr.teacher_id

)

AS

'学科'

FROM

teacher

t

子查询、查询临时表、EXISTS

例子

SELECT

*

FROM

(

SELECT

o.id,

o.student_intention_id,

s.

NAME,

s.area_id,

a.area_name,

s.exam_year,

o.

STATUS,

CASE

o.

STATUS

WHEN

'1'

THEN

'待提交'

WHEN

'2'

THEN

'待指派'

WHEN

'3'

THEN

'已完成'

WHEN

'4'

THEN

'处理中'

END

statusName,

CASE

o.emergency_degree

WHEN

'1'

THEN

'正常'

WHEN

'2'

THEN

'紧急'

WHEN

'3'

THEN

'非常紧急'

END

emergencyDegreeName,

o.emergency_degree,

o.update_time,

(

SELECT

first_lesson_time

FROM

jx_strategy

WHERE

jx_lesson_plan_order_id

=

o.id

AND

STATUS

IN

(2,

7)

AND

first_lesson_time

>

now()

ORDER

BY

first_lesson_time

ASC

LIMIT

1

)

AS

first_time,

(

SELECT

deal_user_id

FROM

jx_strategy

WHERE

jx_lesson_plan_order_id

=

o.id

AND

STATUS

<>

7

AND

deal_user_id

<>

0

ORDER

BY

id

DESC

LIMIT

1

)

AS

deal_user_id

FROM

jx_lesson_plan_order

o

LEFT

JOIN

student

s

ON

s.student_intention_id

=

o.student_intention_id

LEFT

JOIN

area

a

ON

s.area_id

=

a.id

WHERE

o.

STATUS

<>

1

AND

s.phone

=

'18501665888'

AND

o.emergency_degree

=

1

AND

o.

STATUS

=

2

AND

s.exam_year

=

'2015'

AND

o.update_time

>=

'2018-08-14

20:28:55'

AND

o.update_time

<=

'2018-08-14

20:28:55'

)

AS

a

WHERE

1

=

1

AND

a.deal_user_id

=

145316

AND

a.first_time

>=

'2018-08-17

00:00:00'

AND

a.first_time

<=

'2018-08-30

00:00:00'

AND

EXISTS

(

SELECT

*

FROM

jx_strategy

js

WHERE

js.jx_lesson_plan_order_id

=

a.id

AND

js.

STATUS

IN

(2,

7)

AND

js.subject_id

IN

(2,

3)

)

ORDER

BY

a.update_time

DESC

LIMIT

0,

10

update

关联变量条件修改

1、涉及的表关系:

user_info表中的

id_number(身份z号)

teacher表中的birth字段、

关联关系usrer_id

=

teacher_id

2、业务场景：获取用户身份z上的出生日期将出生日期更新在birth字段

UPDATE

teacher

t

INNER

JOIN

(

SELECT

t.teacher_id,

t.birth,

u.id_number,

CONCAT(SUBSTRING(u.id_number,

7,

4),

'-',

SUBSTRING(u.id_number,

11,

2),

'-',

SUBSTRING(u.id_number,

13,

2))

as

birth1,

u.reg_date,

t.exit_time

from

teacher

t

INNER

JOIN

user_info

u

ON

u.user_id

=

t.teacher_id

)

info

on

info.teacher_id

=

t.teacher_id

SET

t.birth

=

info.birth1

WHERE

info.reg_date

>

'2018-08-20

00:00:00'

and

info.id_number

is

not

NULL

and

(info.birth

is

NULL

or

t.birth

=

'')

and

t.is_train

=

1

总结

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