我想要的是向Sqlite android中的现有值添加和删除新值。
我从android文档中读到的是这种方法,但是在我的情况下它不起作用,因为它正在使用提供的新值删除现有值。
这是我的代码:
public boolean updateCigaretteStock(String cigaretteName, int quantity, int totalCost) {
ContentValues values = new ContentValues();
values.put(CigaretteStockEntry.COLUMN_QTY, quantity);
values.put(CigaretteStockEntry.COLUMN_TOTAL_COST, totalCost);
String whereClause = CigaretteStockEntry.COLUMN_CIGARETTE_NAME + " = ?";
String[] whereArgs = {cigaretteName};
int rowAffected = writableDatabase.update(CigaretteStockEntry.TABLE_NAME, values, whereClause, whereArgs);
return (rowAffected > 0);
}
我也尝试过修改方法:
public boolean updateCigaretteStock(String cigaretteName, int quantity, int totalCost) {
ContentValues values = new ContentValues();
values.put(CigaretteStockEntry.COLUMN_QTY, CigaretteStockEntry.COLUMN_QTY + " + " + quantity);
values.put(CigaretteStockEntry.COLUMN_TOTAL_COST, CigaretteStockEntry.COLUMN_TOTAL_COST + " + " + totalCost);
String whereClause = CigaretteStockEntry.COLUMN_CIGARETTE_NAME + " = ?";
String[] whereArgs = {cigaretteName};
int rowAffected = writableDatabase.update(CigaretteStockEntry.TABLE_NAME, values, whereClause, whereArgs);
return (rowAffected > 0);
}
但是它也不起作用。它在列中显示值,例如:
(quantity + new value)
(total_cost + new value)
有什么帮助吗?
最佳答案
如果我正确理解了您的问题,则您尝试沿着以下查询的行增加某些列的值:
UPDATE CigaretteStock
SET
qty = qty + ?,
totalcost = totalcost + ?;
您使用的特定API的问题在于,它仅允许破坏(完全覆盖)给定列中的值。但是,您实际上想使用更新中已经存在的值。
在这种情况下,我建议仅使用SQLite Android的预准备语句API:
String sql = "UPDATE CigaretteStock ";
sql += " SET " + CigaretteStockEntry.COLUMN_QTY + " = " +
CigaretteStockEntry.COLUMN_QTY + " + ?, ";
sql += CigaretteStockEntry.COLUMN_TOTAL_COST + " = " +
CigaretteStockEntry.COLUMN_TOTAL_COST + " + ?";
SQLiteStatement statement = db.compileStatement(sql);
statement.bindDouble(1, quantity);
statement.bindDouble(2, totalCost);
int numberOfRowsAffected = statement.executeUpdateDelete();