oracle複雜查詢備忘

oracle wm_concat(column)函數實現查詢相同id字段，內容以逗號分隔

select id, wmsys.wm_concat(字段名)字段別名  from table group by id

Oracle分組查詢取每組排序後的前N條記錄

SELECT *   
FROM  (
        SELECT 分組的字段名, ROW_NUMBER() OVER(PARTITION BY 分組的字段名 
        ORDER BY 排序的字段名) AS RN FROM 表名
) 
WHERE RN <= 10   得到分組後,數據的前幾條