Question

我收到此错误消息：将varchar值'monthDate'转换为数据类型int时转换失败。

我有这个SQL语句：

String[][] results = lm.SqlSelect("SELECT COUNT(*) FROM members_ WHERE DATEPART(month, DateUnsub_) = 'monthDate' AND DATEPART(year, DateUnsub_) = 2011 AND DATEDIFF(day, DateJoined_, DateUnsub_) <= 30");

我在这里有一个int，其值根据dateLookup值而变化：

switch (dateLookup)
        {
            case "January":
                monthDate = 01;
                break;
            case "February":
                monthDate = 02;
                break;
            case "March":
                monthDate = 03;
                break;
            case "April":
                monthDate = 04;
                break;
            case "May":
                monthDate = 05;
                break;
            case "June":
                monthDate = 06;
                break;
            case "July":
                monthDate = 07;
                break;
            case "August":
                monthDate = 08;
                break;
            case "September":
                monthDate = 09;
                break;
            case "October":
                monthDate = 10;
                break;
            case "November":
                monthDate = 11;
                break;
            case "December":
                monthDate = 12;
                break;
        }

我的问题是 - varchar来自哪里？例如，当我从SQL语句中取出“monthDate”变量并将其替换为数字05时，一切正常。

Answer 1

查询字符串中的

'monthDate'不是变量。

我认为应该是

String[][] results = lm.SqlSelect("SELECT COUNT(*) FROM members_ WHERE DATEPART(month, DateUnsub_) = " +monthDate + " AND DATEPART(year, DateUnsub_) = 2011 AND DATEDIFF(day, DateJoined_, DateUnsub_) <= 30");

考虑使用string.Format()使其更具可读性或更好，参数化命令可以防止SQL注入攻击。

Answer 2

~~您的查询只选择行数。当我查看你的t-sql代码时，你没有选择其他任何东西。~~

看到您的属性后，请使用以下代码;

 switch (dateLookup)
    {
        case "January":
            monthDate = "01";
            break;
        case "February":
            monthDate = "02";
            break;
        case "March":
            monthDate = "03";
            break;
        case "April":
            monthDate = "04";
            break;
        case "May":
            monthDate = "05";
            break;

等等。用英语，在数字前后加上引号。

将varchar转换为月份日期

2 个答案: