感觉自己都已经转为数据库开发了，最近的项目主要是操作本地数据库，一个app有一百多张表，一会join 一会 left join

1 ：五个表 scan ，result ， intrument ，model， vender 表

现在想要查到 result表里面的 rfid ，model表里面的name， vender表里面的name
sql 语句(swift)

let sql = String(format:
                        " select RFIDScanSessionResult.Id," +
                            " RFIDScanSessionResult.rfid," +
                            " Instrument.building," +
                            " Instrument.room," +
                            " Instrument.customerDefineType," +
                            " Site.city," +
                            " vendorModelName," +
                            " standardizedName " +
                            " from ((select *from RFIDScanSessionResult" +
                            " left join RFIDScanSession on RFIDScanSessionResult.sessionId= RFIDScanSession.Id " +
                            " WHERE RFIDScanSessionResult.isHidden = 0 " +
                            " GROUP BY room,Site,building,RFIDScanSessionResult.rfid) as RFIDScanSessionResult " +
                            " left join Instrument on RFIDScanSessionResult.rfid = Instrument.rfidTag " +
                            " left join Model on Instrument.model = Model.Id " +
                            " left join Vendor on Model.vendor = Vendor.Id " +
                            " left join Site on Instrument.site = Site.Id) " +
                            " WHERE RFIDScanSessionResult.isHidden = 0 and " +
                            " (Instrument.isHidden = 0 or Instrument.isHidden is NULL) " +
                        " GROUP BY rfid having count(rfid) > 1 ");

2、 RFIDScanSessionResult表根据RFIDScanSessionResult.sessionId=RFIDScanSession.Id关联表RFIDScanSession 然后根据关联后的表根据RFIDScanSession.site= site.id关联表site，然后根据RFIDScanSessionResult.rfid = '%@' 查找关联后的数据

let sql = String(format:
                    " select %@,%@,%@,%@,%@ " +
                    " from RFIDScanSessionResult " +
                    " Join RFIDScanSession on " +
                    "           RFIDScanSessionResult.sessionId = RFIDScanSession.Id " +
                    " JOIN Site on RFIDScanSession.site = site.id " +
                    " WHERE RFIDScanSessionResult.rfid = '%@' And RFIDScanSessionResult.isHidden = 0" , RFIDScanSessionResult.propertyNameSesssionId,                                                                                                                                                     RFIDScanSession.propertyNameBuilding,                                                                                                                                                                                                                                   RFIDScanSession.propertyNameRoom,Site.propertyNameCity,                                                   RFIDScanSessionResult.propertyNameLastSeen,
                                                              rfid);