MySQL连接两个表并添加列值

Question

我对MySQL的了解不是很深入.如果我有两个表,例如看起来像这样:

Table1
Date        v1  v2  v3
05/01/2010  26  abc 45
05/02/2010  31  def 25
05/03/2010  50  ghi 46

Table2
Date        v1 v2  v3
05/01/2010  42 jkl 15
05/02/2010  28 mno 14
05/03/2010  12 pqr 64

我如何按日期加入查询并获得table1.v1和table2.v1的总和,还有table1.v3和table2.v3的总和？V2应该被忽略.

Answer 1

您可能想要执行以下操作:

SELECT    t1.date, t1.v1 + t2.v1 AS v1_sum,
          t1.v3 + t2.v3 AS v3_sum
FROM      table1 t1
JOIN      table2 t2 ON (t1.date = t2.date);

如果您想要两列的总聚合,您还可以执行以下操作:

SELECT    SUM(t1.v1 + t2.v1) AS v1_sum,
          SUM(t1.v3 + t2.v3) AS v3_sum
FROM      table1 t1
JOIN      table2 t2 ON (t1.date = t2.date);

测试用例:

CREATE TABLE table1 (`date` date, `v1` int, `v3` int);
CREATE TABLE table2 (`date` date, `v1` int, `v3` int);

INSERT INTO table1 VALUES ('2010-05-01', 26, 45);
INSERT INTO table1 VALUES ('2010-05-02', 31, 25);
INSERT INTO table1 VALUES ('2010-05-03', 50, 46);

INSERT INTO table2 VALUES ('2010-05-01', 42, 15);
INSERT INTO table2 VALUES ('2010-05-02', 28, 14);
INSERT INTO table2 VALUES ('2010-05-03', 12, 64);

第一个查询结果:

+------------+--------+--------+
| date       | v1_sum | v3_sum |
+------------+--------+--------+
| 2010-05-01 |     68 |     60 |
| 2010-05-02 |     59 |     39 |
| 2010-05-03 |     62 |    110 |
+------------+--------+--------+

第二个查询结果:

+--------+--------+
| v1_sum | v3_sum |
+--------+--------+
|    189 |    209 |
+--------+--------+