VB.NET 数据库读取错误

Question

I have this SQL sentence for retrieving a specific role (by the column RoleID) from the table Roles:

DBBroker.getInstance.read("SELECT * FROM Roles WHERE RoleID='" & role.roleID & "';")

The thing is that when my program runs the sentence, I obtain this error:

I work with a Microsoft Access Database in which RoleID is defined as Autonumber while in my program it is defined as String. Anyway I tried changing Types but it still fails.

I have too much code in the program so I cannot include it here, but I'm open for any requests regarding a specific part of the program.

Thanks

By the way I worked before on another similar database and the exact same clause did work indeed.

Answer 1

Though you solved your problem,i am answering this just to describe and help guys who visit this page in future

Here's a one line explanation of the issue :

The data type you set for the column in the table of the database is different than the type of value you are passing

For example : In simple words, you have a word and a number , can you add them ? I mean in a mathematical way ? The answer is NO .

Now assuming that your data-type for the RoleID column is Integer but role.RoleId is of type/returns value of type String , then there will be a data-type mismatch as one is an integer and the other is a String .

Now, going through the comments , i see that you've solved your issue.Now, let me explain how you solved it.

Your sql query looks like this :

 "SELECT * FROM Roles WHERE RoleID='" & role.roleID & "';"

Let's point out the main relevant part :

 RoleID='" & role.roleID & "'

Here,before you close the string RoleID= with double quotes, you use ' (single quote).In sql-queries, single quotes are used to declare/give a value(of type STRING ) to the required/given parameter(of the query).

In order to pass an Integer value ,you can pass it without the ' single quote like this :

 RoleID=12345

So, the answer is simple:You were passing some data of type String to a column which expects data/even if the passed value is of type intger but because you were using ' single quotes when passing the values,the quote had converted it to a String ..So, all u have to do(had to do-in your case) is remove the two single quotes( ' )

Hope this helps to enrich your knowledge :)