向数据库添加唯一值 [英] Adding Unique values to database

问题描述

我必须将项目添加到数据库，但是需要确保一项是唯一的.我在这里做什么?

例如，免得说我需要添加100行，每行三列(学校名称idcard_num)

很明显，这里的名称应该唯一，而其余名称可以重复

1我应该创建一个唯一字段，并吐出将抛出给用户的数据库错误吗?
2.添加之前我应该​​检查每个项目吗?

我有这个

I have to add items to database, but need to make sure that one item is unique. what do i do here?

e.g lest say i need to add 100 rows of three columns each (school name idcard_num)

it is obvious that name should be unique here, while the rest can have duplicates

1 should i create a unique field , and spit out the database errors that will be thrown to the user?
2. should i check each items before adding?

i have this

Dim conn As New SQLiteConnection("Data Source=" & DBPath)
        'conn.SetPassword(dbPassword)
        conn.Open()
        Dim cmd As New SQLiteCommand(conn)
        Dim mytransaction As SQLiteTransaction = conn.BeginTransaction()
        Try


            '// insert courses //
            For i = 0 To UBound(oCourses)
                cmd = New SQLiteCommand("INSERT INTO courses ([code]," & _
                    "[title],[unit]) VALUES (@code,@title,@unit)", conn)
                cmd.Parameters.AddWithValue("@code", oCourses(i).Code)
                cmd.Parameters.AddWithValue("@title", oCourses(i).Title)
                cmd.Parameters.AddWithValue("@unit", oCourses(i).Unit)

                'Debug.Print(cmd.CommandText)
                cmd.ExecuteNonQuery()
              Next
            mytransaction.Commit()
            Return Nothing
        Catch ex As Exception
            mytransaction.Rollback()
            Debug.Print(ex.Message)
            Return ex.Message
        Finally
            cmd.Dispose()
            conn.Dispose()
            mytransaction.Dispose()
        End Try

推荐答案

i建议您采用方法 1 ，但不要直接抛出异常.请在对其进行检查之前，先检查它是否与唯一键相关，并显示一条正确的消息，指出名称已存在于数据库."

i will suggest you to go with approach 1 but do not throw the exception as it is.Check it before like if it''s related to unique key display a proper message saying "Name already exists in the database."

在添加之前检查所有项目将是一项开销.我建议你选择第一名.只需确保正确处理异常，以使用户在看到技术错误时不会惊慌失措. :)

Checking all the items before adding will be an overhead. I suggest you go with #1. Just make sure to handle exceptions properly so users will not freak out when they see technical errors. :)

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