Get First Occurrence Of A Row

Here's my table:

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Orders
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UserID | Cost | Item
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Users can make several different orders. I want to only select the row with the first occurrence of a userID. For example:

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Orders
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UserID | Cost | Item
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1 | 3.00 | Box
1 | 6.00 | Candy
2 | 7.00 | Towel
3 | 5.00 | Flower
3 | 6.00 | Candy

Should only select:
1 | 3.00 | Box
2 | 7.00 | Towel
3 | 5.00 | Flower