SQL 字符串大于或小于
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String greater than or less than
提问by mwok
I have the following data:
我有以下数据：
[sequences]
/a1
/a2
/a3
...
/a10
The query SELECT * FROM sequences WHERE nbr <= '/a10'should return the list above, instead it returns:
查询SELECT * FROM sequences WHERE nbr <= '/a10'应该返回上面的列表，而是返回：
[results]
/a1
/a10
How do I make it return all the rows in the above list?
如何让它返回上面列表中的所有行？
回答by GolezTrol
It works as it should. To compare the numeric value, you'll have to convert these to numbers somehow. A good start would be to use substr(yourfieldname, 3) to cut of the/a. Then you can useconvert` to typecast it to int, so your final query will look something like:
它可以正常工作。要比较数值，您必须以某种方式将它们转换为数字。一个好的开始是使用substr(yourfieldname, 3) to cut of the/a . Then you can useconvert` 将其类型转换为 int，因此您的最终查询将类似于：
select * from sequences where convert(int, substr(nbr, 3)) <= 10
Mind that the exact functions and rules for converting strings to ints may very per dbms. This illustrates the general idea, though.
请注意，将字符串转换为整数的确切功能和规则可能非常适合每个 dbms。不过，这说明了总体思路。
回答by user unknown
SELECT *
FROM sequences
WHERE toInt(substring (nbr, 2)) <= 10;
Name and syntax of 'substring'-function and 'toInt' will vary from db-implementation to db-implementation.
'substring'-function 和 'toInt' 的名称和语法会因 db-implementation 到 db-implementation 的不同而不同。
