Excerpted from the game's XML files
Code:
<Civilization_Start_Region_Priority>
<Row>
<CivilizationType>CIVILIZATION_AUSTRIA</CivilizationType>
<RegionType>REGION_HILLS</RegionType>
</Row>
<Row>
<CivilizationType>CIVILIZATION_BRAZIL</CivilizationType>
<RegionType>REGION_JUNGLE</RegionType>
</Row>
<Row>
<CivilizationType>CIVILIZATION_MONGOL</CivilizationType>
<RegionType>REGION_PLAINS</RegionType>
</Row>
<Row>
<CivilizationType>CIVILIZATION_MOROCCO</CivilizationType>
<RegionType>REGION_DESERT</RegionType>
</Row>
<Row>
<CivilizationType>CIVILIZATION_POLAND</CivilizationType>
<RegionType>REGION_PLAINS</RegionType>
</Row>
<Row>
<CivilizationType>CIVILIZATION_SWEDEN</CivilizationType>
<RegionType>REGION_TUNDRA</RegionType>
</Row>
</Civilization_Start_Region_Priority>
But these start region priorities are only biases -- they are not guarantees. Morocco can start nowhere near a Desert for example.
There's no way using XML or SQL that you can
force a civilization to always start in a particular terrain type or region of Hills, Tundra, whatever.