oracle 根据某些条件修改列值
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Modify column value based on some conditions
提问by GoldfishGrenade
Given the following table:
鉴于下表：
... | item | type | ...
... | A | 1 | ...
... | B | 2 | ...
... | A | 2 | ...
... | A | 3 | ...
... | B | 3 | ...
... | A | 2 | ...
Let's call items by pairings (A1, B2, A2, etc). There is an error in the table where an A3 should actually be C3.
让我们通过配对（A1、B2、A2 等）来调用项目。表中有一个错误，其中 A3 实际上应该是 C3。
I want to write a query that will return rows and change the item column to C if the row returned A3.
我想编写一个查询，如果行返回 A3，它将返回行并将项目列更改为 C。
Example query that doesn't work:
不起作用的示例查询：
SELECT (item like 'A' ? (type == 3? 'C' : 'A') : item) as "item", type from table;
My desired output would be:
我想要的输出是：
"item" | type
A | 1
B | 2
A | 2
C | 3
B | 3
A | 2
What is the correct way of doing this? If possible?
这样做的正确方法是什么？如果可能的话？
回答by Olesya Razuvayevskaya
update table tablename
set item='C'
where type=3 and item='A'
If you don't need updating these values in the table, but to get replaced values them as a result of the select, then
如果您不需要更新表中的这些值，而是将它们作为选择的结果替换值，则
select
case when item='A' and type=3 then 'C'
else item
end as newitem, type from tablename
