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with tbl as ( SELECT 1 as id from dual union all SELECT 2 as id from dual union all SELECT 3 as id from dual union all SELECT 4 as id from dual union all SELECT 5 as id from dual union all SELECT 7 as id from dual union all SELECT 10 as id from dual ) SELECT T1.id + 1 AS missing_value FROM (SELECT T2.id, LEAD(T2.id) OVER (ORDER BY T2.id) nextId FROM tbl T2) T1 WHERE T1.nextId > T1.id + 1 UNION SELECT MIN(T.id) + 1 AS missing_value FROM tbl T WHERE MIN(T.id) + 1 NOT IN (SELECT id FROM tbl)