# Section 1: Transaction Isolation Levels

`A1 Dirty read: w1[x] ... r2[x] ... (a1 and c2 in any order)A2 Fuzzy read: r1[x] ... w2[x] ... c2 ... r1[x] ... c1A3 Phantom read: r1[P] ... w2[y in P] ... c2 ... r1[P] ... c1`
`P1 Dirty Read: w1[x]...r2[x]...(c1 or a1)P2 Fuzzy Read: r1[x]...w2[x]...(c1 or a1)P3 Phantom: r1[P]...w2[y in P]...(c1 or a1)`
`P4 Lost update: r1[x]...w2[x]...w1[x]...c1A5A Read skew: r1[x]… w2[x]... w2[y]… c2… r1[y]… (c1 or a1)A5B Write skew: r1[x]… r2[y]… w1[y]… w2[x]… (c1 and c2 occur)A5B2 Write skew 2: r1[P]... r2[P]… w1[y in P]... w2[x in P]...(c1 and c2 occur)`
`r1[x=50] r2[x=50] w2[x=60] c2 w1[x=70] c1`
`(x+y=100) r1[x=50] w2[x=10] w2[y=90] c2 r1[y=90] c1`
`(x+y>=60) r1[x=50] r2[y=50] w1[y=10] c1 w2[x=10] c2`
`(count(P)<=4):r1[count(P)=3],r2[count(P)=3],insert1[x in P],insert2[y in P],c1,c2,`

# Original Source:

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