如何通过char和数字键选择sqlite命令？

Question

sqlite数据库中col的一些值：

a1b2
a2b3
a1b10
a10b1

如果在SQL中使用order by，它将是：

a10b1
a1b10
a1b2
a2b3

我希望像NSNumericSearch这样的objc：

a1b2
a1b10
a2b3
a10b1

如何编写SQL语句？

Answer 1

首先创建自定义整理功能：

int compare_natural(void *data, int len1, const void *str1, int len2, const void *str2) {
    if (str1 && len1 > 0 && str2 && len2 > 0) {
        NSString *s1 = [[NSString alloc] initWithBytesNoCopy:(void *)str1 length:len1 encoding:NSUTF8StringEncoding freeWhenDone:NO];
        NSString *s2 = [[NSString alloc] initWithBytesNoCopy:(void *)str2 length:len2 encoding:NSUTF8StringEncoding freeWhenDone:NO];

        // The use of NSNumericSearch is required for your need.
        // The others are options depending on your needs
        NSComparisonResult res = [s1 compare:s2 options:NSCaseInsensitiveSearch | NSNumericSearch | NSDiacriticInsensitiveSearch];

        return res;
    } else if (str1 && len1 > 0 && (!str2 || len2 == 0)) {
        return -1; // empty strings to the end of the list (optional)
    } else if (str2 && len2 > 0 && (!str1 || len1 == 0)) {
        return 1; // empty strings to the end of the list (optional)
    } else {
        return 0;
    }
}

然后注册自定义整理器。这需要在打开数据库后完成。

// dbRef is your sqlite3 database reference
int rc = sqlite3_create_collation(dbRef, "BYNUMBER", SQLITE_UTF8, NULL, &compare_natural);

然后更新您的查询，使其以“COLLATE BYNUMBER”

结束

  

选择some_col ORDER BY some_col COLLATE BYNUMBER;