mysql - 声明一个表有一个列是两列的乘积

Question

表格产品

id  name   price   quantity   total

1     food    50      1         50
2     drink   20      2         40
3     dress   100     3         300

如何声明一个表，其中一列是两列的乘积？

我有这个代码:

CREATE TABLE [dbo].[Orders] (
    [Id]          INT        IDENTITY (1, 1) NOT NULL,
    [ProductName] NCHAR (70) NULL,
    [Price]       INT        NULL,
    [Quantity]    INT        NULL,
    [Total] INT NULL, 
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

Answer 1

听起来你想要一个 VIEW .

他们的例子正是你所描述的

mysql> CREATE TABLE t (qty INT, price INT);
mysql> INSERT INTO t VALUES(3, 50);
mysql> CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;
mysql> SELECT * FROM v;
+------+-------+-------+
| qty  | price | value |
+------+-------+-------+
|    3 |    50 |   150 |
+------+-------+-------+