Java derby SQL整数查询

Question

Please take a look at my code snippet below. What I am trying to achieve is querying the database for any results equal to the user input. It is querying SDS_NUMBER column which is an integer column.

When I execute the query it returns the following exception:

java.sql.SQLSyntaxErrorException: Comparisons between 'INTEGER' and 'CHAR (UCS_BASIC)' are not supported. Types must be comparable. String types must also have matching collation....etc.

I understand that it is saying I am trying to compare an integer to char but I have tried to cast from examples I found on the net but no luck. Also I tried parseInt and using that value in the search but I still can't get it to work. Please advise what I am doing wrong and excuse my newbies to all of this.

     } else if (tmp == "sdsNumber") {
        try {
            Integer sdsNum = Integer.parseInt(val);
            String sql = "SELECT SDS_NUMBER, PRODUCT_NAME, PROPER_SHIPPING_NAME FROM APP.MASTER WHERE SDS_NUMBER = '"+sdsNum+"'";
            pst = conn.prepareStatement(sql);
            pst.executeQuery();
            jTable1.setModel(DbUtils.resultSetToTableModel(rs));

        } catch (Exception e) {
            e.printStackTrace(System.out);
            JOptionPane.showMessageDialog(null, e);

        }

Master table creation:

CREATE TABLE MASTER
(
    id integer NOT NULL GENERATED ALWAYS AS (START WITH 1, INCREMENT BY 1)
,   SDS_NUMBER integer UNIQUE
,   PRODUCT_NAME varchar(100)
,   PRODUCT_DESCRIPTION varchar(500)
,   SDS_FILE_PATH varchar(50)
,   USE_STATUS BOOLEAN
,   DATA_UPDATED date
,   PROPER_SHIPPING_NAME varchar(100)
,   SIGNAL_WORD varchar(20)
,   CONSTRAINT MASTER_PRIMARY_KEY PRIMARY KEY (id)
);

Answer 1

Remove the single quote "'"+sdsNum+"'" to be a number

Her ara Example by using preparedStatement

String sql = "SELECT SDS_NUMBER, PRODUCT_NAME, PROPER_SHIPPING_NAME FROM APP.MASTER WHERE SDS_NUMBER = ?";
pst = conn.prepareStatement(sql);
pst.setInt(1, sdsNum);
ResultSet rs = pst.executeQuery(sql);
while (rs.next()) {
    int SDS_NUMBER = rs.getInt("SDS_NUMBER");
    String PRODUCT_NAME= rs.getString("PRODUCT_NAME");
    ....

}

Answer 2

it seems you're wrapping an integer in quotes

SDS_NUMBER = '"+sdsNum+"'"

probably what you want is

SDS_NUMBER = ?

and then set the number with your PreparedStatement instead of concatenating strings

see http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html

and

http://docs.oracle.com/javase/7/docs/api/java/sql/PreparedStatement.html#setInt%28int,%20int%29

Answer 3

} else if ("sdsNumber".equals(tmp)) {

after I changed the first line to this everything works. I dont fully understand what difference that made and if someone could shine some light on it, I would appreciate it as I am slowly learning this.