SQL 字符串与数字等于比较与null的判断逻辑

sku_cid3是int类型，sku_cid3!=null 永远都是null

SELECT   cast(sku_brand_id as int) AS brand_code,   cast(sku_cid3 as int) AS third_cate_code,   count(1) AS ad_pv FROM ad.ad_base2_impression WHERE dt='2019-08-15' AND sku_brand_id != '0'   AND sku_cid3 IS NOT NULL AND sku_cid3 <> '' GROUP BY sku_brand_id, sku_cid3