I was wondering if it was possible to multiply two columns and if so how would this take place
我想知道是否有可能增加两列，如果是这样的话，这将是怎样发生的
Suppose I have a table
假设我有一张桌子
a b
1 4
2 5
3 6
Could I do something like
我能做点什么吗
SELECT a *b from table
Would this multiply the contents row by row then store it in a new column
这会将内容逐行相乘，然后将其存储在新列中
Are these result right
这些结果是否正确
4
10
18
3 个解决方案
#1
12
That query would multiply the values, but it wouldn't "store it in a new column" To store it you would have to issue an update statement.
该查询将乘以这些值，但它不会“将其存储在新列中”要存储它，您必须发出更新语句。
Assuming you add a new column ("c") to your table you could do:
假设您向表中添加了一个新列（“c”），您可以执行以下操作：
update table
set c = a * b
If all you need is the new column in a result set, without modifying the underlying table you could:
如果您需要的只是结果集中的新列，而无需修改基础表，您可以：
select a, b, (a*b) as c from table
#2
1
Yes you can perfectly do that.
是的，你可以做到这一点。
update
更新
To clarify: The query and output you mentioned in your question are correct.
澄清一下：您在问题中提到的查询和输出是正确的。
#3
0
Rather than storing a calculated column in a base table, consider a viewed table:
而不是将计算列存储在基表中，考虑查看表：
CREATE VIEW MyView
AS
SELECT a, b,
a * b AS my_calc
FROM MyTable;
#1
12
That query would multiply the values, but it wouldn't "store it in a new column" To store it you would have to issue an update statement.
该查询将乘以这些值，但它不会“将其存储在新列中”要存储它，您必须发出更新语句。
Assuming you add a new column ("c") to your table you could do:
假设您向表中添加了一个新列（“c”），您可以执行以下操作：
update table
set c = a * b
If all you need is the new column in a result set, without modifying the underlying table you could:
如果您需要的只是结果集中的新列，而无需修改基础表，您可以：
select a, b, (a*b) as c from table
#2
1
Yes you can perfectly do that.
是的，你可以做到这一点。
update
更新
To clarify: The query and output you mentioned in your question are correct.
澄清一下：您在问题中提到的查询和输出是正确的。
#3
0
Rather than storing a calculated column in a base table, consider a viewed table:
而不是将计算列存储在基表中，考虑查看表：
CREATE VIEW MyView
AS
SELECT a, b,
a * b AS my_calc
FROM MyTable;