1、查詢專案位址address為空的建立人姓名和專案名稱；
select
a.name,
b.name
from
user a,
project b
where a.id=b.user_id
and b.address ='';
select a.name,c.name1 from user a inner join (
select b.user_id,b.name as name1 from project b where b.address='') as c
on a.id=c.user_id;
2、查詢建立專案最多的使用者id、姓名和專案數量
select
a.id,
a.name,
count(b.user_id)
from
user a,
project b
where a.id=b.user_id
group by b.user_id
order by count(b.user_id) desc limit 1;
select a.id,a.name,c.total from user a inner join (
select b.user_id,count(b.user_id) as total from project b group by b.user_id order by count(b.user_id) desc limit 1) as c
on a.id=c.user_id;
3、查詢建立時間在2015至2023年之間的專案id、專案名稱和建立時間
select id,name,createtime from project where createtime between "2015-01-01" and "2018-12-31";
select id,name,createtime
from project
where substring(createtime,1,4) >= 2015
and substring(createtime,1,4) <= 2018
4、查詢沒有在天津和上海建立專案的使用者id和姓名
select
a.id,
a.name
from
user a,
(select distinct(b.user_id) from project b where b.address !='上海' and b.address!='天津')
as e
where
a.id=e.user_id;
select a.id,a.name from user a where a.id in (
select distinct(b.user_id) from project b where b.address !='上海' and b.address!='天津');
5、查詢在天津和上海都建立了專案的使用者id和使用者姓名
select
a.id,
a.name
from
user a,
(select distinct c.user_id from
(select b.user_id from project b where b.address='天津' ) as c
inner join (select p.user_id from project p where p.address='上海' ) as d
on c.user_id =d.user_id
as e
where
a.id=e.user_id;
select a.id,a.name from user a where a.id in (
select distinct(b.user_id) from project b where b.user_id in
(select b.user_id from project b where b.address ='上海') and b.address='天津');
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