Question

我想要获得最大数量的值。但它没有用。

    drqry = "SELECT max(num) FROM tbCVinfo WHERE cvabbrv LIKE '%" & abbrv & "%' and `year` LIKE '%" & year & "%'"
    'drqry = "SELECT max(cvno) FROM tbCVinfo WHERE cvno LIKE '%" & cvstr & "%'"

    cmd2.CommandText = drqry
    cmd2.Connection = con

    dr = cmd2.ExecuteReader

    Dim result As String = ""

    If dr.Read() Then
        dr.Close()

        cv = Convert.ToInt32(cmd2.ExecuteScalar())  ''''i am having an error in this part. it says "Object cannot be cast from DBNull to other types." upon checking all datas in the database, I don't have null values
        cv = cv + 1
        If cv >= 0 And cv <= 9 Then
            result = "000" & cv

Answer 1

如果您尝试获取最大数量，则第一个查询应改为：

drqry = "SELECT max(num) FROM tbCVinfo WHERE cvabbrv LIKE '%" & abbrv & "%' and `year` LIKE '%" & year & "%'"

Answer 2

这是我的代码。是的，它现在正在运行。非常感谢您的帮助。

    drqry = "SELECT max(num) FROM tbCVinfo WHERE cvno LIKE '%" & cvstr & "%'"

    cmd2.CommandText = drqry
    cmd2.Connection = con

    Dim result As String = ""

    cv = Convert.ToInt32(cmd2.ExecuteScalar())

我想获得最大数量

2 个答案: