简单点，不知道这样可不可以。
SELECT layerid,ChangeMold,COUNT(ChangeMold) FROM table_name
GROUP BY layerid,ChangeMold

select count(*),layid,changeMold from tbl group by layid,changeMold

SELECT 
layerid,
sum(case when changeMold='U' then 1 else 0 end) changeMold_U,
sum(case when changeMold='A' then 1 else 0 end) changeMold_A
FROM table_name 
GROUP BY layerid;

如果 要 统计这种大文件 的话 。还是都查出来 然后再处理数组方便点（sql比较弱 ）

select layerid,changeMold,count(*) as num from TABLE where layerid in (select layerid from TABLE group by layerid) group by changeMold; 这条sql的性能很不好