mysql - 每当我提交表单时都会出现 sql 错误

Question

我正在尝试从 mySQL 数据库获取数据并将其存储到我的 arrayList 中。但是，每当我运行这组代码时，我都会收到此错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'displayname LIKE '%A%'' at line 1

但是，我没有使用任何关键字，我为通配符运算符添加了单引号。我的sql语句哪里做错或者遗漏了？

String sql = "SELECT * FROM azq.registration WHERE userId NOT IN (SELECT friendId FROM azq.friendlist WHERE userId ="
                        + session.getAttribute("userId")
                        + ") AND userId !="
                        + session.getAttribute("userId")
                        + "AND displayname LIKE '%" + searchText + "%'";
                // create the java statement
                Statement st = conn.createStatement();

                // execute the query, and get a java resultset
                ResultSet rs = st.executeQuery(sql);

                // iterate through the java resultset
                while (rs.next()) {
                    Friends newList = new Friends();
                    newList.setFirstName(rs.getString("firstName"));
                    newList.setLastName(rs.getString("lastName"));
                    newList.setUserId(rs.getString("userId"));
                    newList.setDisplayname(rs.getString("displayname"));

                    resultList.add(newList);
                }
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SQLException e) {
                e.printStackTrace();
            }

Answer 1

您必须在AND之前添加一个空格:

                + session.getAttribute("userId")
                    + " AND displayname LIKE '%" + searchText + "%'";