如何防止在sqlite数据库中插入重复值(如果重复则覆盖) [英] How to prevent to insert duplicate value in sqlite database (if duplicate then overwrite)
问题描述
我在我的数据库中创建了两个表,在两个表中我同时插入值,现在我想做的是,我想在第二个表中插入记录,但条件是,如果有是两条相同的记录,那么我只想插入一条记录而不是重复值,在第二个表中有两个字段,一个是 id,第二个是 category,当用户插入两个相同的类别时那个时候我只想插入一个条目,下面是我的代码无法正常工作,它插入所有记录接受重复值..
I had created two table in my database, In both table I am inserting value at the same time, now what I want to do is that, I want to insert record in second table, but the condition is that, if there is two same record then I want insert only one record not duplicate value, In second table there is two field one is id and second is category, when user insert two same category that time I want to insert only one entry, below is my code which is not working properly, It insert all record accept duplicate value..
public long InsertCat(String idd, String cat)
{
try
{
SQLiteDatabase db;
long rows = 0;
db = this.getWritableDatabase();
ContentValues Val = new ContentValues();
Val.put("IDD", idd);
Val.put("Category", cat);
Cursor c = db.rawQuery("SELECT * FROM " + TABLE_CATEGER + " WHERE Category='"+cat+"'",null);
while(c.moveToNext())
{
if(c.getString(0).equals(cat))
{
flag=true;
}
}
if(flag==true)
{
rows=db.update(TABLE_CATEGER, Val, "Category='"+cat+"'" , null);
System.out.print(rows);
db.close();
}
if(flag==false)
{
rows = db.insert(TABLE_CATEGER, null, Val);
System.out.print(rows);
db.close();
}
return rows; // return rows inserted.
} catch (Exception e) {
return -1;
}
}
推荐答案
将所有值放入 ContentValues
中,然后在 writableDatabase
Put all your values inside ContentValues
and then call this on writableDatabase
db.insertWithOnConflict(tableName, null, contentValues,SQLiteDatabase.CONFLICT_REPLACE);
你只需要这部分代码
SQLiteDatabase db;
long rows = 0;
db = this.getWritableDatabase();
ContentValues Val = new ContentValues();
Val.put("IDD", idd);
Val.put("Category", cat);
rows = db.insertWithOnConflict(tableName, null, contentValues,SQLiteDatabase.CONFLICT_REPLACE);
insertWithOnConflict
方法遵循最后一个参数作为发现重复行时的反应算法.为了找到重复的行,主键必须发生冲突.如果所有这些都满足该行肯定会被替换 :-/如果不是其他问题..
insertWithOnConflict
methods follows the last parameter as the reaction algorithm when an duplicate row is Found. And for a duplicate row to be found, the primary keys has to clash. If all this satisfys the row would surely get Replaced :-/ If not something else is going wrong..
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