java 连接数据库错误总结
昨天第一天接到任务，把数据库中name相同的行，将第一条中列不为空的内容复制到第二条为空的对应位置。
public static void main(String[] args) {// TODO Auto-generated method stubString driver = "com.mysql.jdbc.Driver";String url = "jdbc:mysql://localhost:3306/brew_operation_db?characterEncoding=UTF-8";String userName = "root";String password = "123";ArrayList<String> Imagepath = new ArrayList<String>();ArrayList<String> name = new ArrayList<String>();ArrayList<Integer> id = new ArrayList<Integer>();ArrayList<Integer> ids = new ArrayList<Integer>();try {Class.forName(driver);Connection conn = DriverManager.getConnection(url, userName, password);Statement statement = conn.createStatement();String sql = "select * from brew group by name having count(*)>1";ResultSet rs = statement.executeQuery(sql);while(rs.next()){name.add(rs.getString("name"));id.add(rs.getInt("id"));Imagepath.add(rs.getString("Imagepath")) ;}rs.close();statement.close();for (int j = 0; j < id.size(); j++) {String sqla = "select * from brew where name = '"+name.get(j)+"' and id <> "+id.get(j);Statement statement1 = conn.createStatement();ResultSet rs1 = statement1.executeQuery(sqla);if(rs1.next()){ids.add(rs1.getInt("id"));}}for (int i = 0; i < ids.size(); i++) {String sqlb = "update brew set Imagepath = '"+Imagepath.get(i)+"' where id = "+ids.get(i);Statement statement2 = conn.createStatement();int s = statement2.executeUpdate(sqlb);}} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}}