本文介绍了在SQL中添加一个临时列,其中值取决于另一列的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有这张桌子:
ID | name | result | -------------------- 1 | A | 1 | -------------------- 2 | B | 2 | -------------------- 3 | C | 1 | -------------------- 1 | A | 2 | -------------------- 4 | E | 2 | --------------------我想在| result |旁边添加一个新的临时列,其中result = 1的值应为100,而result = 2的值应为80,因此应如下所示:
I want to add a new temporary column next to |result|, and where result=1 the value should be 100, and where result=2 the value should be 80 so it should look like this:
ID | name | result | NewColumn| ------------------------------- 1 | A | 1 | 100 | ------------------------------- 2 | B | 2 | 80 | ------------------------------- 3 | C | 1 | 100 | ------------------------------- 1 | A | 2 | 80 | ------------------------------- 4 | E | 2 | 80 | -------------------------------如何在SQL中查询呢?
How can I query this in SQL ?
推荐答案使用 SELECT的列列表中的CASE表达式-像这样:
Use a CASE expression in your SELECT's column list - something like this:
SELECT ID, name, result, CASE WHEN result = 1 THEN 100 WHEN result = 2 THEN 80 ELSE NULL END AS NewColumn FROM YourTable根据需要添加其他WHEN表达式或更改ELSE表达式.
Add additional WHEN expressions or alter the ELSE expression as needed.
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在SQL中添加一个临时列,其中值取决于另一列
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