SQL选择总和条件2表？

Question

I have 2 table

Table Connection
----------------------------------------
|  ID       |  Member_ID  |  Connection| 
----------------------------------------
|  1        |  100        |  22        | 
----------------------------------------
|  2        |  101        |  15        | 
----------------------------------------
|  3        |  102        |  19        | 
----------------------------------------
|  4        |  103        |  21        | 

Table Member
---------------------------
|  ID         |  Status     |
---------------------------
|  100        |  0          | 
----------------------------
|  101        |  1          | 
----------------------------
|  102        |  1          | 
---------------------------
|  103        |  0          |   

I want to get sum of Connection has status =1 . The result in example should be 15+19 = 34 .

Answer 1

Here is an example of how to write this query using generic SQL:

SELECT
    SUM(Connection.Connection) AS ConnectionSum
FROM
    Connection
JOIN
    Member ON Connection.Member_ID = Member.ID
WHERE
    Member.Status = 1;

Answer 2

This should work fine for you :

select sum(Connection) as Total_connection 
        from Connection where ID in 
( select ID from member where status = 1 );

Answer 3

This is in reference to MySQL and MariaDB databases:

SELECT SUM(Connection) 
       FROM Connection 
       WHERE Member_ID = ALL (SELECT ID FROM Member WHERE Status = 1);

OR

SELECT SUM(Connection) 
       FROM Connection 
       WHERE Member_ID IN (SELECT ID FROM Member WHERE Status = 1);

Answer 4

SELECT SUM(cn. connection ) sumresult FROM connection AS cn WHERE cn. member_id
IN (SELECT em.id FROM member AS em WHERE em. status =1);

I hope it can help you as your require

Answer 5

You are getting an error because the subquery returns more than one ID(multiple records) where as an equal operator can take only one value. Use an IN operator instead of Equal operator and your error will be removed.

select sum(connection) from connection 
where connection.member_id IN (select id from member where status=1)