Javascript SQLite插入和删除查询出现错误，但不是SELECt查询

我正在使用SQLite（WebSQL）在Cordova移动应用程序中本地保存表单数据。
下面的代码适用于同一表的

SELECT

query，但不适用于INSERT或DELETE查询。

它将错误输出为：

无法准备语句

const usersDB = {
    add: function (firstname, lastname, dob, email, phone, city, state, country) {
        databaseHandler.db.readTransaction(
            function (tx) {
                tx.executeSql(
                    "INSERT INTO users(firstname, lastname, dob, email, phone, city, state, country) VALUES(?, ?, ?, ?, ?, ?, ?, ?)",
                    [firstname, lastname, dob, email, phone, city, state, country],
                    function (tx, results) {
                        console.log('User has been saved');
                    },
                    function (tx, error) {
                        console.log('ERROR: Failed to add user', error);
                    }
                );
            }
        );
    },
    selectAll: function (listUsers) {
        databaseHandler.db.readTransaction(
            function (tx) {
                tx.executeSql(
                    "SELECT * FROM users ORDER BY firstname",
                    [],
                    function (tx, results) {
                        listUsers(results);
                    },
                    function (tx, error) {
                        console.log('ERROR: Failed to list users', error);
                    }
                );
            }
        );
    }
}

我搜索了几十个讨论表单，但找不到关于此问题的解决方案。
我们将提前感谢您的帮助

只读事务用于只读。写事务允许读和写。读事务由SELECT语句启动，写事务由CREATE、DELETE、DROP、INSERT或UPDATE等语句启动（统称为“写语句”）

.readTransaction（）

用于只读查询，

.transaction（）

用于写查询。
因此，在我的情况下，我应该这样使用它们：

const usersDB = {
    add: function (firstname, lastname, dob, email, phone, city, state, country) {
        databaseHandler.db.transaction( // Write mode
            function (tx) {
                tx.executeSql(
                    "INSERT INTO users(firstname, lastname, dob, email, phone, city, state, country) VALUES(?, ?, ?, ?, ?, ?, ?, ?)",
                    [firstname, lastname, dob, email, phone, city, state, country],
                    function (tx, results) {
                        console.log('User has been saved');
                    },
                    function (tx, error) {
                        console.log('ERROR: Failed to add user', error);
                    }
                );
            }
        );
    },
    selectAll: function (listUsers) {
        databaseHandler.db.readTransaction( // read-only mode
            function (tx) {
                tx.executeSql(
                    "SELECT * FROM users ORDER BY firstname",
                    [],
                    function (tx, results) {
                        listUsers(results);
                    },
                    function (tx, error) {
                        console.log('ERROR: Failed to list users', error);
                    }
                );
            }
        );
    }
}