我正在尝试获取最大值

2guxujil 于 2021-06-24 发布在 Mysql

关注(0)|答案(2)|浏览(263)

我想得到最大值。但它不起作用。

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

mysql vb.net

来源：https://stackoverflow.com/questions/50033778/i-am-trying-to-get-the-max-number

2条答案

按热度按时间

r8xiu3jd1#

这是我的密码。是的，它现在正在运行。非常感谢你的帮助。

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())

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5fjcxozz2#

如果您试图获取最大值，则第一个查询应该是：

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

赞(0）回复(0）举报 2021-06-24

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我正在尝试获取最大值

2条答案

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