DB-UCR/Lab#6_A.sql at main · JirlOP/DB-UCR · GitHub

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USE C12565
SELECT * FROM LLEVA

-- Escenario 1: Nivel de aislamiento read uncommitted

-- 6
set implicit_transactions off; -- default
set transaction isolation level read uncommitted;
begin transaction t1;
PRINT @@TRANCOUNT
Select avg(Nota) from Lleva;

-- 8
Select avg(Nota) from Lleva;

-- 10
Select avg(Nota) from Lleva;
Commit transaction t1;

-- Escenario 2: Nivel de aislamiento read committed

-- 12
set implicit_transactions off;
set transaction isolation level read committed;
begin transaction t3;
Select avg(Nota) from Lleva;

-- 14
Select max(Nota) from Lleva;

-- 16
Commit transaction t3;

-- Escenario 3: Nivel de aislamiento repeatable read

-- 18
set implicit_transactions off;
set transaction isolation level repeatable read;
begin transaction t5;
Select avg(Nota) from Lleva;

-- 20
Select avg(Nota) from Lleva;
commit transaction t5;

-- Escenario 4: Nivel de aislamiento serializable

-- 22
set implicit_transactions off;
set transaction isolation level serializable;
begin transaction t7;
Select avg(Nota) from Lleva;

-- 24
Select avg(Nota) from Lleva;
commit transaction t7;