-- 原始資料
-- a   111
-- b   222
-- a   333
-- a   444
-- b   555
-- 最終結果
-- a   111*333*444

SELECT 
L4.L_TIME
,MAX(SUBSTR(L4.分組內容,2)) 最終欄位值
FROM(
		SELECT 
		L3.L_TIME
		,SYS_CONNECT_BY_PATH(L3.L_CONTENT,'*') AS 分組內容
		FROM(
				SELECT
				L2.L_TIME
				,L2.L_CONTENT
				,L2.L_TIME||L2.分組內編號 AS 分組欄位加編號,L2.L_TIME||(L2.分組內編號-1) AS 上級分組欄位加編號
				FROM(
						SELECT 
						L1.L_TIME   -- 分組依據
						,L1.L_CONTENT    -- 同一列中 要合併的不同行 的值
						,ROW_NUMBER() OVER (PARTITION BY L1.L_TIME ORDER BY L1.L_CONTENT ASC) 分組內編號 
						FROM LOGS L1
				) L2
		) L3
		START WITH L3.上級分組欄位加編號 LIKE '%0' 
		CONNECT BY PRIOR L3.分組欄位加編號=L3.上級分組欄位加編號
) L4
 
WHERE L_TIME='111'
GROUP BY L4.L_TIME

-- ROW_NUMBER() OVER(PARTITION BY A ORDER BY B DESC) 新列名
-- 根據A分組，在分組內部根據B排序，而此函式計算的值就表示每組內部排序後的順序編號（組內連續的唯一的)

-- SYS_CONNECT_BY_PATH 函式： 第一個引數是形成樹形式的欄位，第二個引數是父級和其子級分隔顯示用的分隔符
-- CONNECT BY PRIOR 是標示父子關係的對應
-- START WITH 代表你要開始遍歷的的節點

------------------------------------------------------------------------------------------
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附上建表語句：

DROP TABLE LOGS;
CREATE TABLE LOGS (
L_ID VARCHAR2(32) NOT NULL ,
L_CONTENT VARCHAR2(512)  ,
L_TIME VARCHAR2(32) ,
L_USER VARCHAR2(32) ,
PRIMARY KEY (L_ID)
); 

COMMENT ON TABLE LOGS IS '日誌表';
COMMENT ON COLUMN LOGS.L_ID IS '日誌ID';
COMMENT ON COLUMN LOGS.L_CONTENT IS '日誌內容';
COMMENT ON COLUMN LOGS.L_TIME IS '時間';
COMMENT ON COLUMN LOGS.L_USER IS '操作人';

INSERT INTO LOGS (L_ID, L_CONTENT, L_TIME, L_USER)  VALUES ('123', '黑啊', '111', '12345');
INSERT INTO LOGS (L_ID, L_CONTENT, L_TIME, L_USER)  VALUES ('124', '白啊', '222', '123456');
INSERT INTO LOGS (L_ID, L_CONTENT, L_TIME, L_USER)  VALUES ('125', '黑白啊', '111', '1234567');
INSERT INTO LOGS (L_ID, L_CONTENT, L_TIME, L_USER)  VALUES ('126', '白白啊', '111', '12345');
INSERT INTO LOGS (L_ID, L_CONTENT, L_TIME, L_USER)  VALUES ('127', '嘿嘿啊', '222', '123456');