条件语句，骨料跨多个表

Question

我有表如下所示：

`units` 
+----+------+-------+---------------+-------+ 
| id | tech | jobID |  city  | units | 
+----+------+-------+---------------+-------+ 
| 1 | 1234 | 8535 | San Jose  |  3 | 
| 2 | 1234 | 8253 | San Francisco |  4 | 
| 3 | 1234 | 2457 | San Francisco |  5 | 
| 4 | 1234 | 8351 | Mountain View |  8 | 
+----+------+-------+---------------+-------+ 

，并使用这些数据做一些计算的看法：

`total` 
+----+--------+------+-------+ 
| id | name | tech | total | 
+----+--------+------+-------+ 
| 1 | Dan | 1234 | 12 | 
| 2 | Dan SF | 1234 | 12 | 
+----+--------+------+-------+ ... 

我的问题是，我试图总结Dan在旧金山完成的单位数量以及他在其他地方完成的单位数量（需要专门跟踪SF中完成的单位数量）。但是，我不确定如何在我的选择查询中执行此操作，并且如果您查看当前的总表，则会看到两个总值都只是将所有单位相加，而不考虑城市。

我希望得到以下几点：

`total` 
+----+--------+------+-------+ 
| id | name | tech | total | 
+----+--------+------+-------+ 
| 1 | Dan | 1234 | 11 | 
| 2 | Dan SF | 1234 |  9 | 
+----+--------+------+-------+ ... 

我需要帮助写我的选择，因为我不能确定如何使用CASE以获得期望的结果。我试过以下内容：

SELECT otherTable.name AS name, units.tech AS tech, 
(CASE WHEN City = 'SAN FRANCISCO' THEN SUM(units) 
     ELSE SUM(units) 
) AS total 
FROM units, otherTable 
GROUP BY name 

但很明显，这是行不通的，因为我没有区分两个集合中的城市。

任何帮助，非常感谢。

编辑：我目前的观点的SELECT查询（与加盟信息）如下：

`otherTable` 
+----+--------+------+-----------+ 
| id | name | tech | otherInfo | 
+----+--------+------+-----------+ 
| 1 | Dan | 1234 | ...... | 
+----+--------+------+-----------+ 

Answer 1

：

SELECT otherTable.name, units.tech, SUM(units.units) 
FROM units 
LEFT JOIN otherTable ON otherTable.tech = units.tech 
GROUP BY name 

至于otherTable，它只是每个高科技ID与一个名字相关联首先，看起来您的基本查询是错误的。 units和otherTable之间并没有任何关系，但我不知道足够。

对我来说，看起来很奇怪，你希望它分成行而不是列，但你可以请执行以下操作：

SELECT otherTable.name AS name, units.tech AS tech, 
SUM(units) AS total 
FROM units, otherTable 
-- not sure if this section should exclude 'SAN FRANCISO' or not 
GROUP BY name 
UNION ALL 
SELECT otherTable.name || ' SF' AS name, units.tech AS tech, 
SUM(units) AS total 
FROM units, otherTable 
WHERE City = 'SAN FRANCISCO' 
GROUP BY name 

这将使你

+--------+------+-------+ 
| name | tech | total | 
+--------+------+-------+ 
| Dan | 1234 | 11 | 
| Dan SF | 1234 |  9 | 
+--------+------+-------+ 

或者，如果你想单独的列，你可以这样做

SELECT otherTable.name AS name, units.tech AS tech, 
SUM(units) AS total, 
SUM(CASE WHEN City = 'SAN FRANCISCO' THEN units 
     ELSE 0 
) AS sf_total 
FROM units, otherTable 
GROUP BY name 

这将使你

+--------+------+-------+----------+ 
| name | tech | total | sf_total | 
+--------+------+-------+----------+ 
| Dan | 1234 | 11 |  9 | 
+--------+------+-------+----------+