Android sqlite插入记录(如果不存在)

我想在sqlite表中添加一个新项(Cheese),但前提是它不存在.我只在表中有两列：_id(KEY_ROWID_PR)和product_name(KEY_NAME_PR).

我一直在尝试使用这些代码,但它给了我一个错误：

public void populate_base_lists2(String tablename, String item) {
        ourDatabase.execSQL("INSERT INTO " + tablename + " (" + KEY_NAME_PR + ") SELECT * FROM (SELECT " + item  + ") WHERE NOT EXISTS (SELECT " + KEY_NAME_PR + " FROM " + tablename + " WHERE " + KEY_NAME_PR + " = " + item + ") LIMIT 1;");
}

03-11 17:27:20.972: E/AndroidRuntime(658): Caused by:
android.database.sqlite.SQLiteException: no such column: Cheese:
INSERT INTO PR_Dairy_Products (product_name) SELECT * FROM (SELECT
Cheese) WHERE NOT EXISTS (SELECT product_name FROM PR_Dairy_Products
WHERE product_name = Cheese) LIMIT 1;

代码来自：MySQL: Insert record if not exists in table

没有这样的列：干酪,好吧,我把那部分更改为KEY_NAME_PR,然后错误是相同的,但没有这样的列：product_name.该栏肯定存在.

更重要的是,我需要对此代码进行一些解释.我在一定程度上有sql知识,但我无法得到这个.

谢谢

解决方法:

我认为你可能需要在变量项出现时单引号,因为它的值不是列名.
试试这段代码：

public void populate_base_lists2(String tablename, String item) {
ourDatabase.execSQL("INSERT INTO " + tablename +
" (" + KEY_NAME_PR + ") SELECT * FROM (SELECT '" + item  + "')
WHERE NOT EXISTS (
SELECT " + KEY_NAME_PR +
" FROM " + tablename + " WHERE " + KEY_NAME_PR + " = '" + item + "'
) LIMIT 1;");
}

希望有所帮助.