SQL Server 2017

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CREATE TABLE TableX
(MM001 NVARCHAR(20),MM002 NVARCHAR(60));

INSERT INTO TableX 
VALUES
(1 , N'55.5X46X50cm 120個/板;18箱/板'),
(2 , N'155.5X46X50cm 20個/板;300瓶/板'),
(3 , N'255.5X46X50cm 4120個/板;1000罐/板');

SELECT *
FROM TableX;

MM001
MM002

1
55.5X46X50cm 120個/板;18箱/板

2
155.5X46X50cm 20個/板;300瓶/板

3
255.5X46X50cm 4120個/板;1000罐/板

SELECT 
left(MM002,CharIndex(' ',MM002))
+ Right(MM002,len(MM002)+ 1 - CharIndex(';',MM002)) MM002
from TableX

MM002

55.5X46X50cm ;18箱/板

155.5X46X50cm ;300瓶/板

255.5X46X50cm ;1000罐/板

select replace(MM002,
substring(MM002,CharIndex(' ',MM002),CharIndex(';',MM002) - CharIndex(' ',MM002))
,'') MM002
from TableX

MM002

55.5X46X50cm;18箱/板

155.5X46X50cm;300瓶/板

255.5X46X50cm;1000罐/板

MM001	MM002
1	55.5X46X50cm 120個/板;18箱/板
2	155.5X46X50cm 20個/板;300瓶/板
3	255.5X46X50cm 4120個/板;1000罐/板