汇总联接表中的行内容

Question

I have two tables here.

• log (stands for logbook)
• act (stands for actions)

log

contains columns: logid , userid , actid

act

contains columns: actid , amount

Amount stands for an amount of points (eg 50 of 700 or 5) the user ( userid ) receives when the corresponding actid is inserted in the logbook ( log ).

What I'm trying to achieve is that when you search for userid 1, that all rows from log where userid = 1 are selected. Then, from these selected log -rows, the actid s should be looked up in the table act , and the amount s should be summed.

In short:

• select log -rows where userid = 1

• take all the actids from these rows

• find the matching amount in the act table

• sum all these amounts

I started with this query:

SELECT log.logid, log.userid, log.actid, act.actid, act.amount
FROM log
    JOIN act
        ON act.actid = log.actid
WHERE log.userid = '1'

This got me a table with (among other things)

userid | amount

---1----|--20---

---1----|--40---

---1----|---5---

---1----|--10---

Now I would like to sum all these amounts and echo the total, but unfortunately I can't find a working query for this.

EDIT:

I used the query that Naruto provided me to sum these amounts. This works like a charm now! The query:

SELECT log.userid, sum(act.amount) FROM log JOIN act ON act.actid = log.actid WHERE log.userid = '1'

The next thing that I'm trying is to get not only the summed amount from the user with userid = 1 , but also from the other users in the user -table. After that, I'd like to use these summed amounts in the following query:

$result = $mysqli->query("SELECT * FROM `db`.`user` ORDER BY `summed_amount` DESC");

In which summed_amount is the summed amount generated by Naruto's query.

Answer 1

MySQL has an Aggregate function called sum() which can sum all the records.

So your query will be

SELECT log.userid, sum(act.amount) FROM log JOIN act ON act.actid = log.actid WHERE log.userid = '1'

http://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_sum

Answer 2

To get sum of all users by a single query use group by clause.Here it will calculate sum of amaount for each user and return the result.

SELECT log.userid, sum(act.amount) FROM log JOIN act ON act.actid = log.actid group by log.userid

Edit:- To get order by desc

SELECT log.userid, sum(act.amount) FROM log JOIN act ON act.actid = log.actid group by log.userid order by sum(act.amount) desc