MySQL 在mysql中创建表，其中一列包含另外两列值的总和
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/6805498/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Create table in mysql with one column containing sum of another two columns value
提问by riyana
Is it possible in mysql to create a table with a column that combines two column values? something like this:
是否可以在 mysql 中创建一个包含两个列值的列的表？像这样：
create table test1 (
number1 int,
number2 int,
total int DEFAULT (number1+number2)
);
or like this :
或像这样：
CREATE TABLE `Result` (
`aCount` INT DEFAULT 0,
`bCount` INT DEFAULT 0,
`cCount` = `aCount` + `bCount`
);
回答by TehShrike
It is not possible to do that exactly, but you can create a view based on a query that combines them:
不可能完全做到这一点，但您可以根据组合它们的查询创建一个视图：
CREATE VIEW `my_wacky_view` AS
SELECT `number1`, `number2`, `number1` + `number2` AS `total`
FROM `test1`;
I would avoid actually storing the combined data in a table, unless you're going to be running lots of queries that will reference the combined data in their WHERE clauses.
我会避免将组合数据实际存储在表中，除非您将运行大量查询，这些查询将在其 WHERE 子句中引用组合数据。
回答by Edgar Velasquez Lim
You can create a trigger on the table so MySQL calculates and automatically inserts that column value every time an INSERT happens on your test1 table. Make the table:
您可以在表上创建一个触发器，以便每次在 test1 表上发生 INSERT 时，MySQL 都会计算并自动插入该列值。制作表格：
create table test1 (
number1 int,
number2 int,
number3 int
);
Then create a Trigger
然后创建触发器
CREATE TRIGGER triggername AFTER INSERT
ON test1
FOR EACH ROW
UPDATE test1 SET NEW.number3=NEW.number1+NEW.number2
MySQL documentation on triggers: http://dev.mysql.com/doc/refman/5.0/en/create-trigger.html
关于触发器的 MySQL 文档：http: //dev.mysql.com/doc/refman/5.0/en/create-trigger.html
Make sure to add the ON UPDATE trigger as well if you expect UPDATES to happen to the rows.
如果您希望 UPDATES 发生在行上，请确保也添加 ON UPDATE 触发器。
回答by shabbychef
I had this issue as well. From Edgar Velasquez' answer here, and the answer to this question, I stumbled upon this incantation:
我也有这个问题。从 Edgar Velasquez 的回答和这个问题的回答中，我偶然发现了这个咒语：
CREATE TRIGGER insert_t BEFORE INSERT
ON test1
FOR EACH ROW
SET NEW.number3=NEW.number1+NEW.number2;
CREATE TRIGGER insert_t_two BEFORE UPDATE
ON test1
FOR EACH ROW
SET NEW.number3=NEW.number1+NEW.number2;
This works for me on MySQL 5.6.22.
这在 MySQL 5.6.22 上对我有用。
回答by Seb
Little fix :
小修复：
CREATE TRIGGER triggername BEFORE INSERT
ON test1
FOR EACH ROW
SET NEW.number3=NEW.number1+NEW.number2
