珠海h5建站,成都哪些公司做网站好,北京网站建设公司房山华网,南昌网站建设怎么样我有一个名为stars的MySQL表,其中一个字段是id_num,默认值为NULL.我想通过java中的PreparedStatement选择id_num不为NULL的所有记录.现在我正在尝试这个#xff1a;private final String idStarsSQL select * from stars where id_num is not ?;...preparedStat…我有一个名为stars的MySQL表,其中一个字段是id_num,默认值为NULL.我想通过java中的PreparedStatement选择id_num不为NULL的所有记录.现在我正在尝试这个private final String idStarsSQL select * from stars where id_num is not ?;...preparedStatement (PreparedStatement) connection.prepareStatement(idStarsSQL);preparedStatement.setString(1, NULL);set preparedStatement.executeQuery();但它不起作用.解决方法:private final String idStarsSQL select * from stars where id_num is not NULL;你不需要PreparedStatement.从我的角度来看,PreparedStatement应该用于带参数的SQL语句.使用带参数的SQL语句的优点是,您可以使用相同的语句,并在每次执行时为其提供不同的值.Statement statement con.createStatement();ResultSet result statement.executeQuery(select username, age, nickname from user where nickname is not NULL);List allUserNullNickname new ArrayList();while(result.next()){User user new User();user.setUsername(result.getString(username));user.setAge(result.getInt(age));allUserNullNickname.add(user);}System.out.println(All user without nickname:);allUserNullNickname.stream().forEach(user - System.out.println(username: user.getUsername() Age: user.getAge()));标签java,mysql,select,prepared-statement,notnull,java来源 https://codeday.me/bug/20190622/1265765.html
