Code:
INSERT INTO dbo._RefMonster_AssignedItemDrop
(RefMonsterID, RefItemID, DropGroupType, OptLevel, DropAmountMin, DropAmountMax, DropRatio, RefMagicOptionID1, CustomValue1, RefMagicOptionID2, CustomValue2, RefMagicOptionID3, CustomValue3, RefMagicOptionID4, CustomValue4, RefMagicOptionID5, CustomValue5, RefMagicOptionID6, CustomValue6, RefMagicOptionID7, CustomValue7, RefMagicOptionID8, CustomValue8, RefMagicOptionID9, CustomValue9, RentCodeName)
SELECT ID, 25834, 0, 0, 1, 1, 1, '0.5', 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'NULL', 0, 'xxx'
FROM dbo._Refobjcommon with(NOLOCK) where [Service] = 1 and Codename128 like 'MOB_%%'
All mobs with drop ratio 50% (50% chance to drop from the killed mob, if you want to change this > change '0.5' to 1 (100%) 0.2 (20%) etc...