这样呢?
SELECT yearAge
FROM (SELECT DateDiff(yyyy, cast(出生日期 as datetime), GetDate()) AS yearAge
FROM 客户
WHERE IsDate(出生日期) = 1) tableA
WHERE (yearAge > 0)
SELECT DateDiff(yyyy, convert(datetime,出生日期), GetDate()) AS yearAge
FROM 客户
WHERE IsDate(出生日期) = 1 and DateDiff(yyyy, convert(datetime,出生日期), GetDate()) >0