MySQL SQL - 如何获取单元格的特定值？
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SQL - how to get specific value of cell?
提问by user1386966
Fist time using SQL and already confused. I have a table :
第一次使用 SQL 并且已经感到困惑。我有一张桌子：
A | B
--------
a | 6
b | 10
c | 12
I want to filter it by using string comparison, but getting the value of the second column :
我想通过使用字符串比较来过滤它，但获取第二列的值：
myNum = SELECT B WHERE A ='a'
At the end I want the value of myNum to be 6.
最后，我希望 myNum 的值为 6。
Just can't get it right... any help would be very appreciated!
只是无法正确...任何帮助将不胜感激！
回答by Raghvendra Parashar
You need to specify table name.
您需要指定表名。
SELECT B from table_name WHERE A = 'a';
回答by Andy Lester
You need the table name.
您需要表名。
SELECT b FROM tablename WHERE A='a';
SELECT b FROM tablename WHERE A='a';
回答by Laurence
Firstly, you need to include the table name. Secondly, you need to use := for assignment and @ as a prefix to a variable:
首先，您需要包含表名。其次，您需要使用 := 进行赋值，并使用 @ 作为变量的前缀：
Select
@myNum := B
From
test
Where
A = 'a';
This will also return a result set. If you just want variable assignment, you can use Select ... Into
这也将返回一个结果集。如果你只想变量赋值，你可以使用Select ... Into
Select
B
into
@myNum
From
test
Where
A = 'a'
These assume your variable is within MySQL, if you are using a different programming language then there will a different method.
这些假设您的变量在 MySQL 中，如果您使用不同的编程语言，那么会有不同的方法。
