MySQL从2个表运行总计

Question

是否可以从2个表中执行运行总计或累计和的子查询？结果将保存为“新值”。

第一张桌子：

var changes = R.Db(DbName).Table(TableName)
    //.changes()[new {include_states = true, include_initial = true}]
    .Changes()
    .RunChanges<JObject>(conn);

changes.IsFeed.Should().BeTrue();

var observable = changes.ToObservable();

//use a new thread if you want to continue,
//otherwise, subscription will block.
observable.SubscribeOn(NewThreadScheduler.Default)
    .Subscribe(
        x => OnNext(x),
        e => OnError(e),
        () => OnCompleted()
    );

第二张表：

CREATE TABLE data2 ( date1 DATE,mt int);

INSERT INTO data2 VALUES ('2018-01-01',76564);
INSERT INTO data2 VALUES ('2018-02-01',140005);
INSERT INTO data2 VALUES ('2018-03-01',231973);
INSERT INTO data2 VALUES ('2018-04-01',340085);

预期结果：

Answer 1

假设new value字段基于日期在两个表中总计运行，则下面的查询应该对您有用。

SELECT t.date, t.mt, 
         (@running_total := @running_total + t.mt) AS new_value
FROM (
  SELECT date1 date, mt from data2
  UNION ALL
  SELECT date1 date, mt from bajet
) AS t
JOIN (SELECT @running_total := 0) r
ORDER BY t.date;