Db2 11.1

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CREATE TABLE t(
  name   VARCHAR(5) NOT NULL
  ,year   INTEGER  NOT NULL
  ,var1   VARCHAR(1) NOT NULL
  ,var2   VARCHAR(1) NOT NULL
);
INSERT INTO t(name,year,var1,var2) VALUES ('John',2001,'a','b');
INSERT INTO t(name,year,var1,var2) VALUES ('John',2002,'a','a');
INSERT INTO t(name,year,var1,var2) VALUES ('John',2003,'a','b');
INSERT INTO t(name,year,var1,var2) VALUES ('Mary',2001,'b','a');
INSERT INTO t(name,year,var1,var2) VALUES ('Mary',2002,'a','b');
INSERT INTO t(name,year,var1,var2) VALUES ('Mary',2003,'b','a');
INSERT INTO t(name,year,var1,var2) VALUES ('Alice',2001,'a','b');
INSERT INTO t(name,year,var1,var2) VALUES ('Alice',2002,'b','a');
INSERT INTO t(name,year,var1,var2) VALUES ('Alice',2003,'a','b');
INSERT INTO t(name,year,var1,var2) VALUES ('Bob',2001,'b','a');
INSERT INTO t(name,year,var1,var2) VALUES ('Bob',2002,'b','b');
INSERT INTO t(name,year,var1,var2) VALUES ('Bob',2003,'b','a');
select * from t;


NAME
YEAR
VAR1
VAR2


John
2001
a
b

John
2002
a
a

John
2003
a
b

Mary
2001
b
a

Mary
2002
a
b

Mary
2003
b
a

Alice
2001
a
b

Alice
2002
b
a

Alice
2003
a
b

Bob
2001
b
a

Bob
2002
b
b

Bob
2003
b
a


select *
from (
  select y.*, max(v) over(partition by name) as maxv,
    max(rn) over(partition by name) as maxrn
  from (
    select x.*, 
      sum(case when lag1 = var1 then 0 else 1 end) 
        over(partition by name order by year) as v,
      row_number() over(partition by name order by year) as rn
    from (
      select t.*,
        lag(var1) over(partition by name order by year) as lag1,
        lag(var2) over(partition by name order by year) as lag2
      from t
    ) x
  ) y
) z
where maxv > 1 and v = 2 or maxv = 1 and rn = maxrn


NAME
YEAR
VAR1
VAR2
LAG1
LAG2
V
RN
MAXV
MAXRN


Alice
2002
b
a
a
b
2
2
3
3

Bob
2003
b
a
b
b
1
3
1
3

John
2003
a
b
a
a
1
3
1
3

Mary
2002
a
b
b
a
2
2
3
3

NAME	YEAR	VAR1	VAR2
John	2001	a	b
John	2002	a	a
John	2003	a	b
Mary	2001	b	a
Mary	2002	a	b
Mary	2003	b	a
Alice	2001	a	b
Alice	2002	b	a
Alice	2003	a	b
Bob	2001	b	a
Bob	2002	b	b
Bob	2003	b	a