ALTER TABLE table_a ADD e_column NUMBER;

UPDATE table_a
SET e_column = COALESCE(
MAX(CASE WHEN tpfg = 1 THEN TO_NUMBER(TO_CHAR(month, 'YYYYMM')) END)
OVER (PARTITION BY emid),
200001
);

ALTER TABLE table_a ADD e_column NUMBER;

UPDATE table_a a SET e_column = nvl((select month from table_a b where b.emid=a.emid and b.tpfg=1),'200001');

ALTER TABLE table_a ADD e_column NUMBER;

update table_a set e_column= month where tpfg=1;

update table_a set e_column = 200001 where tpfg != 1;