我在iOS应用程序中使用SQLite,我使用FMDB作为包装。这是我的数据库架构:使用FMDB获取复杂数据
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 *code;
@property (nonatomic,copy) NSString *name;
@end
比如我获取数据库中的所有报价是这样的:
- (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]
}
这是工作,但它需要时间,因为我正在使用许多SQL请求来获取所有优惠和相应的市场。
我可以避免很多SQL
请求获取相应市场的所有优惠吗?谢谢您的回答
感谢您的回答。您能否给出一个代码示例如何执行一个SQL请求以获取每个报价的报价和相应的市场? (我不明白如何解析同一个对象FMResultSet以获得优惠和市场 – samir