英文:
Why the sqlite cursor in android returns different values?
问题
我有一个简单的查询，你可以看到一行：
SELECT substr(..., 10, 6) as X
如果我使用 cursor.getInt(...)，我得到 1048（"错误" 值）
如果我使用 cursor.getString(...)，我得到 "002030"（这是正确的）。
那么，是什么让 SQLite 将 "002030" 解析为 1048？
我是否需要每次都将其作为字符串获取并自己解析？
谢谢。
英文:
I have simple query, where you can see a row:
SELECT substr(..., 10, 6) as X
If I use cursor.getInt(...) I get 1048 (the "wrong" value)
If I use cursor.getString(...) I get "002030" (which is correct).
So, what makes sqlite parse "002030" as 1048?
Do I have to get it as string and parse it myself every time?
Thank you.
答案1
得分: 2
substr()函数返回一个字符串，所以你应该使用cursor.getString()来检索该值，它会返回正确的结果。
如果你希望结果是一个整数，你必须在你的SQL代码中进行转换，可以显式地这样做：
SELECT cast(substr(..., 10, 6) as integer) as X
或者隐式地这样做：
SELECT substr(..., 10, 6) + 0 as X
结果将是整数2030，没有前导的0。
至于你得到的奇怪的1048，Java认为以0开头的数字文字是八进制数字，所以：
int x = 002030;
将1048赋给了x，这是八进制数字2030的十进制表示。
英文:
The function substr() returns a string, so you should retrieve the value with cursor.getString(), which returns the correct result.<br/>
If you want the result as an integer, you must convert it in your sql code, either explicitly:
SELECT cast(substr(..., 10, 6) as integer) as X
or implicitly:
SELECT substr(..., 10, 6) + 0 as X
The result will be the integer 2030 without the leading 0s.<br/>
As for the strange 1048 that you get, Java considers numeric literals starting with 0 as octal numbers, so:
int x = 002030;
assigns 1048 to x which is the decimal representation of the octal number 2030.
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