如何删除SQLite数据库中的特定行

问题描述

我是android的新手，我无法理解sqlite数据库中的删除功能.我已使用字符串

I am new to android and i am having trouble understanding the delete function in sqlite database.I have created my database using the string

private static final String TABLE_NAME="NameInfo";
    private static final String POSITION_DB ="_id";
    private static final String Name_DB ="name";
    private static final String JSONOBJECT_DB="json";
    private static final String TIMESTAMP_DB="time";
    private static final String USERRATING_DB="userrating";
    private static final String DATABASE_NAME ="database.db";
private final String createDb ="create table if not exists "+TABLE_NAME +" ("
                + POSITION_DB + " integer primary key, "
                + NAME_DB + " text not null, "
                + JSONOBJECT_DB + " text not null, "
                + USERRATING_DB + " text not null, "
                +TIMESTAMP_DB + " text not null); ";

现在，当我启动我的应用程序时，我希望删除超过2天之前添加的所有行

Now when i start my app i want that all rows that were added more than 2 days ago should be deleted

所以我打算做这样的事情

so i am planning to do something like this

long currentdate =new date().getTime();

然后检查表的每一行的currenttime-Long.Valueof(TIMESTAMP_DB)字段之间的差异，如果大于2 * 24 * 60 * 60，则删除该行

and than check the difference between currenttime-Long.Valueof(TIMESTAMP_DB) field for each rows of the table and if it is more than 2*24*60*60 than delete that row

有人可以告诉我如何使用以下功能实现以上功能

Can someone please tell me how can i use the below function to achieve the above

public int delete (String table, String whereClause, String[] whereArgs)

我不确定我应该在whereClause和whereArgs中写什么.

i am not sure what should i write in whereClause and whereArgs.

如果有人能告诉我一个比这更好，更简单的方法，我将非常感激.

I would be really grateful if someone can tell me a even better and simple approach than this.

PS我也尝试通过execSQL语句执行操作，但无法编写完整的查询通过database.execSQL("Delete * from "+TABLE_NAME+" WHERE = "+currentdate - Long.ValueOf(?) >2*24*60*60 ;")

PS i also tried doing by execSQL statement but was not able to write the complete queryby database.execSQL("Delete * from "+TABLE_NAME+" WHERE = "+currentdate - Long.ValueOf(?) >2*24*60*60 ;")

谢谢.

推荐答案

您可以使用如下查询:

db.execSQL("DELETE FROM " + TABLE_NAME +
           " WHERE " + currentdate + " - " + TIMESTAMP_DB + " > 2*24*60*60");

对于update方法，在whereClause参数的WHERE子句中编写SQL表达式； whereArgs仅对于字符串值是必需的:

For the update method, write the SQL expression in the WHERE clause in the whereClause parameter; whereArgs is needed only for string values:

db.update(TABLE_NAME, currentdate + " - " + TIMESTAMP_DB + " > 2*24*60*60", null);

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