mysql的多表查询-笛卡尔表

emp一共有13条dept的有4个条件

//查询自己需要的字段
select ename,sal,dname,emp.deptno from emp,dept where emp.deptno = dept.deptno;

 

 

 

/*查询分类*/
select member_id,count(member_id) as num from orders group by member_id having num =1;

 

/*查询orders表中只出现过一次的member_id，并且创建时间是在8月份*/
select member_id,amount,quantity,buy_quantity,order_num,partner_member_id,created_at,updated_at,count(member_id) as num from orders group by member_id having num =1 

and created_at >= '2023-08-01' and created_at <='2023-09-01 00:00';

 

/*另外一种写法，时间在两者时间*/
select member_id,amount,quantity,buy_quantity,order_num,partner_member_id,created_at,updated_at,count(member_id) as num from orders group by member_id having num =1 

and created_at between '2023-08-01' and '2023-09-01 00:00';

 

查询数据

SELECT sum(send_money) from send_calculate_detail WHERE member_id = 19 and created_at>='2023-09-01 00:00';

select * from send_calculate where member_id = 19 and created_at >= '2023-09-01 00:00' order by created_at asc;

SELECT sum(send_money) from send_calculate WHERE member_id = 19 and created_at>='2023-09-01 00:00';