phoneGap Android - 填充数据库一次“错误处理 SQL：1”

Question

如果数据库存在，我会尝试避免填充数据库，但是当我尝试在代码中取消此行时，我得到 "Error processing SQL:1"

tx.executeSql('DROP TABLE IF EXISTS DEMO');

这是我的全部填充函数

 function populateDB(tx) {
        tx.executeSql('DROP TABLE IF EXISTS DEMO');
        tx.executeSql('CREATE TABLE IF NOT EXISTS DEMO (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, word TEXT NOT NULL');
        tx.executeSql('INSERT INTO DEMO (id, word) VALUES ("1", "Apple")');
        tx.executeSql('INSERT INTO DEMO (id, word) VALUES ("2", "Orange")');

    }

Answer 1

你为什么不使用

CREATE TABLE IF NOT EXISTS DEMO  (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, kword TEXT NOT NULL, eword TEXT NOT NULL, pronoun TEXT NOT NULL, level INTEGER NOT NULL)

Answer 2

您的函数存在一系列问题，这些问题在下面得到纠正。它现在应该可以工作了。

    function populateDB(tx) {
        isTableExists(tx, "DEMO", function(status) {
            if (!status) {
                alert("table not exist, creating one");
                tx.executeSql('CREATE TABLE DEMO (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, kword TEXT NOT NULL, eword TEXT NOT NULL, pronoun TEXT NOT NULL, level INTEGER NOT NULL)');
                tx.executeSql('INSERT INTO DEMO (kword, eword, pronoun, level) VALUES ("Apple", "", "", 1)');
                tx.executeSql('INSERT INTO DEMO (kword, eword, pronoun, level) VALUES ("Orange", "", "", 2 )');
            } else {
                alert("table exist, dropping for test");
                tx.executeSql('DROP TABLE DEMO');
            }
        });
    }

    function isTableExists(tx, tableName, callback) {
        tx.executeSql('SELECT * FROM DEMO', [], function(tx, resultSet) {
            if (resultSet.rows.length <= 0) {
                callback(false);
            } else {
                callback(true);
            }
        }, function(err) {
            callback(false);
        });
    }