refer to with clause
WITH AVG_WT_GENDER AS
(SELECT GENDER,AVG(WEIGHT) AS AVG_WT_SEX FROM CHILDSTAT GROUP BY GENDER
),
AVG_WT_OVERALL AS
(SELECT AVG(AVG_WT_SEX) AS AVG_WT_ALL FROM AVG_WT_GENDER
)
SELECT a.*
FROM CHILDSTAT a
WHERE a.WEIGHT >=
(SELECT AVG_WT_ALL FROM AVG_WT_OVERALL
)