[Vladimir]

struct CreatureDisplayInfoExtraEntry
{
    uint32 DisplayExtraId; // 0 m_ID CreatureDisplayInfoEntry::m_extendedDisplayInfoID
    uint32 Race; // 1 m_DisplayRaceID

You can get race by display id with extanded info

[Added]
In fact, in DBCStores.h exist special function for this:

MANGOS_DLL_SPEC uint32 GetCreatureModelRace(uint32 model_id);