Question

我想检查数据库中是否已有5行，但我不能使用execSQL方法调用SELECT，因为它返回void，而其他任何东西似乎都不适合if语句。那么有一个简单的解决方法还是我必须采取另一种方式？

//add a new row to the database
public void addProduct(Products product){

    SQLiteDatabase db =  this.getWritableDatabase();
    if(db.execSQL("SELECT Count * FROM " + TABLE_PRODUCTS) == 5){
        ContentValues values = new ContentValues();
        values.put(COLUMN_PRODUCTNAME, product.get_productname());
        db.insert(TABLE_PRODUCTS, null, values);
        db.close();
    }
}

Answer 1

试试这个

module carona

open util/ordering[Time]

sig Time {}

sig Car {
    passengers : set Passager
}

one sig UFCG{
    students: set Student -> Time

}

abstract sig Student{
    region: Region -> Time
}

sig Owner extends Student{
    ownerCar : Car 
}

sig Passager extends Student{
}

abstract sig Region{ }

one sig Norte,Sul,Leste,Oeste,Centro extends Region{ }



fact Owner{
    all o: Owner | #o.ownerCar = 1
}

fact Passager{
    all p:Passager | one p.~passengers  
}

fact Car{
    all c:Car| one c.~ownerCar
    all c:Car| #c.passengers <= 4
    all c:Car| c.passengers.region=(c.~ownerCar).region 

}

fact UFCG {
    all passager: Passager, ufcg : UFCG, t:Time | passager in (ufcg.students).t
    all owner: Owner, ufcg: UFCG,t:Time | owner in (ufcg.students).t
} 

fact Traces{
    init[first]
    all pre: Time-last | let pos = pre.next |
    lone u:UFCG|
    some s:Student|
    addStudent[s,u,pre,pos]
}



pred init[t:Time]{
    one u:UFCG | no (u.students).t 
}



pred addStudent[s:Student, u: UFCG, before, after: Time]{

    (s !in (u.students).before) 
    (u.students).after = (u.students).before + s
}

Answer 2

结果可能是这样的：

public int addProduct()
{
String selectQuery = "SELECT * FROM TABLE_PRODUCTS";           
SQLiteDatabase database = this.dbOpenHelper.getReadableDatabase();
Cursor c = database.rawQuery(selectQuery, null);
c.moveToFirst();
int total = c.getCount();
c.close();

return total;
}

调用SQLiteDatabase方法在＆＃34;中使用SELECT语句＆＃34;声明？

2 个答案: