Example – Inconsistent read
•
•ClearOut(p1,s1)          MakeSale(p1,s2,60)
•Query InStore: qty is 30
•Add 30 to WarehouseQty: 10->40
•                                      update row 2: 65->5
•                                      find sum: 75
•                                           // no need to insert
•                                           // row in Order
•Update row 1, setting it to 0
•COMMIT
•                                       COMMIT
•
etc
etc
etc
60
s1
p2
65
s2
p1
30
s1
p1
Initial state of InStore, Product
Final state of InStore, Product
Integrity constraint is false:
Sum for p1 is only 45!
etc
etc
etc
60
s1
p2
5
s2
p1
0
s1
p1
etc
etc
etc
44
etc
p2
10
etc
p1
etc
etc
etc
44
etc
p2
40
etc
p1