[英]MySql - Create view by merging two tables based on values
我有两个表:
financials_standalone ('fin_id', 'attr_id', 'year', 'value');
financials_consolidated ('fin_id', 'attr_id', 'year', 'value');
('fin_id', 'attr_id', 'year') is the unique key
financials_consolidated表将具有除financials_standalone之外的数据。
例如:
financials_standalone
| fin_id | attr_id | year | value |
---------------------------------------
| fin01 | pe | 2016 | 33.23 |
| fin02 | pe | 2016 | 12.52 |
financials_consolidated
| fin_id | attr_id | year | value |
---------------------------------------
| fin02 | pe | 2016 | 20.41 |
现在,我要将两个表合并为一个视图:-如果该行存在于合并中,则选择该行,否则从Financials_standalone表中选择该行。
所以最终的视图输出应该是这样的
financials_data_view
| fin_id | attr_id | year | value |
---------------------------------------
| fin01 | pe | 2016 | 33.23 |
| fin02 | pe | 2016 | 20.41 |
我无法找到大小写或左外部联接的解决方案。 如何获得此视图输出?
LEFT JOIN financials_standalone
上financials_consolidated
摆脱价值financials_consolidated
在所有情况下,并使用COALESCE()函数,返回从表2的第一个非空值。 然后执行一个联合以从financials_consolidated
获取这些记录,以从该表中获取另一个记录中不存在的记录。 如果不是这种情况,则您不需要联合。
select fs.fin_id, fs.attr_id, fs.year, coalesce(fc.value, fs.value) as val
from `financials_standalone` fs
left join `financials_consolidated` fc
on fs.fin_id=fc.fin_id
and fs.attr_id=fc.attr_id
and fs.year=fc.year
union
select fc.fin_id, fc.attr_id, fc.year, fc.value
from `financials_consolidated` fc
left join `financials_standalone` fs
on fs.fin_id=fc.fin_id
and fs.attr_id=fc.attr_id
and fs.year=fc.year
where fs.fin_id is null
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.