在Java中使用SQL语句插入数字数据类型

Question

I am writing a method which allows users to store their data within my database.

The problem I have is storing a numeric datatype in my database, for a user's ID.

Firstly, how can I tell if the ID number is auto-incrementing? These are it's properties:

Type: Numeric
Column size: 4
Decimal digits: 0
Part of primary key: true
Part of an index: true
Position: 1

I'm sure I read somewhere that, setting it as part of an index (true) allows for auto-incrementation. Can anyone confirm?

More importantly, when inserting data into my table I receive an error stating:

Columns of type 'NUMERIC' cannot hold values of type 'CHAR'. 

This is a snippet of my insert code (I can reveal more if need be):

Statement pStatement = conn.createStatement();
String selectSQL = ("INSERT INTO APP.PERSON VALUES ('" + '3' + "','" + user + "','" + pass + "','" + fName + "','" + sName + "','" + sQuestion + "','" + sAnswer + "') ");
pStatement.executeUpdate(selectSQL);

As you can see I am setting ID (the first value), to 3 manually. I believe this is throwing up the error and would like to know how to insert a numeric value, using the INSERT command.

I am coding in Java, using Netbeans 7.3 Beta 2, on Mac OS X Mountain Lion. I am using a Derby database.

Answer 1

Hey bro I suggest u to use prepareStatement

String template = "INSERT INTO APP.PERSON VALUES (YOUR,TABLE,COLLUMN,NAME) values (?,?,?,?)";
           PreparedStatement stmt = yourConnection.prepareStatement(template);

So if your want to set your ID as an integer, let java do it with

       stmt.setInt(1, ID);
       stmt.setString(2, user);
       stmt.setString(3, fName);
       stmt.executeUpdate();

I dont know how is your table structure but this is an example if you want to use int use stmt.setInt(1, 3);

1--> position that u set up in string template

3--> maybe u want to hard coded the ID

here is my example pattern to use prepareStatement

String name = "shadrach"
Double price = "100.00"
int qty = 3;
    String template = "INSERT INTO PRODUCT (NAME,PRICE,QTY) values (?,?,?)";
                PreparedStatement stmt = connection.prepareStatement(template);
                stmt.setString(1, name);
                stmt.setDouble(2, price);
                stmt.setInt(3, qty);
                stmt.executeUpdate();

Answer 2

You shouldn't put single quotes around the number. I'm not sure of the types of the other column data types but anything that is numeric should not contain the single quotes.

Statement pStatement = conn.createStatement();

String selectSQL = ("INSERT INTO APP.PERSON VALUES (3,'" + user + "','" + pass + "','" + fName + "','" + sName + "','" + sQuestion + "','" + sAnswer + "') ");

 pStatement.executeUpdate(selectSQL);

You should also look into switching this up to use a PreparedStatement , concatenating Strings to execute SQL will leave you vulnerable to a SQL injection attack. Prepared statements will help mitigate this risk.

Answer 3

You're inserting the character 3 when the table expects a number.

You can tell if a column is auto-increment, using the ResultSetMetaData 's isAutoIncrement method. Hope that helps....