CREATE TABLE Offer (code TEXT PRIMARY KEY NOT NULL,name TEXT);

CREATE TABLE OffreMarket (codeOffer TEXT NOT NULL,codeMarket TEXT NOT NULL,FOREIGN KEY(codeOffer) REFERENCES Offer(code),FOREIGN KEY(codeMarket) REFERENCES Market(code));

CREATE TABLE Market (code TEXT PRIMARY KEY NOT NULL,name TEXT);

我的模型对象：

@interface Offer : NSObject
@property (nonatomic,copy) NSString *code;
@property (nonatomic,copy) NSString *name;
@property (nonatomic,copy) NSArray *markets;
@end

@interface OffreMarket : NSObject
@property (nonatomic,copy) NSString *codeOffer;
@property (nonatomic,copy) NSString *codeMarket;
@end

@interface Market : NSObject
@property (nonatomic,copy) NSString *name;
@end

例如,我正在获取数据库中的所有商品,如下所示：

- (NSArray *)offers {
// Open database

NSMutableArray *offers = [NSMutableArray new];

FMResultSet *resultSet = [database executeQuery:@"SELECT * FROM Offer"];
while ([resultSet next]){

   Offer *offer = [Offer new];
   offer.code = [resultSet stringForKey:@"code"];
   offer.name = [resultSet stringForKey:@"name"];

   // Get the markets for each offer
   FMResultSet *marketResultSet = [database executeQuery:@"SELECT * FROM  OffreMarket WHERE codeOffer = ?",offer.code];

   NSMutableArray *offers = [NSMutableArray new];
   while ([marketResultSet next]) {
      OffreMarket *offerMarket = [OffreMarket new];
      ....
     [offers addObject:offerMarket];
   }

  market.offers = [offers copy];
}

return [offers copy]

}

这是有效的,但需要时间,因为我使用许多sql请求来获取所有商品和相应的市场.

我可以避免许多sql请求来获取相应市场的所有商品吗？谢谢你的回答