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如何在MySQL的新列中获得两列之间的差异？

2024-05-01 04:27:05 421

让我们首先创建一个带有列的表，我们将为其计算新列中的差-

mysql> create table DemoTable
(
   Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   LowValue int,
   HighValue int
);

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable(LowValue,HighValue) values(100,200);
mysql> insert into DemoTable(LowValue,HighValue) values(300,700);
mysql> insert into DemoTable(LowValue,HighValue) values(1000,2000);

以下是使用select语句显示表中所有记录的查询-

mysql> select *from DemoTable;

这将产生以下输出-

+----+----------+-----------+
| Id | LowValue | HighValue |
+----+----------+-----------+
| 1  | 100      | 200       |
| 2  | 300      | 700       |
| 3  | 1000     | 2000      |
+----+----------+-----------+
3 rows in set (0.00 sec)

这是获取2列之间的差的查询-

mysql> select tbl.Id,tbl.LowValue,tbl.HighValue, 
   HighValue-LowValue AS DifferenceBetweenTwoColumns from DemoTable tbl;

这将产生以下输出-

+----+----------+-----------+-----------------------------+
| Id | LowValue | HighValue | DifferenceBetweenTwoColumns |
+----+----------+-----------+-----------------------------+
| 1  | 100      | 200       | 100                         |
| 2  | 300      | 700       | 400                         |
| 3  | 1000     | 2000      | 1000                        |
+----+----------+-----------+-----------------------------+
3 rows in set (0.00 sec)

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如何在MySQL的新列中获得两列之间的差异？

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