select ProductName，EncapsulationType from WorkOrder

CREATE TABLE t1
(
    col VARCHAR(50)
)
INSERT INTO t1
SELECT 'OM011 OC' UNION ALL
SELECT 'GC012 UT' UNION ALL
SELECT 'GC011 UT1' UNION ALL
SELECT 'GC013 UT1_GC013' UNION ALL
SELECT 'GC015 UT1_GC015'
SELECT * FROM t1

SELECT CASE WHEN CHARINDEX('_',col)>0 THEN LEFT(col,CHARINDEX('_',col)-1) ELSE col END
FROM t1

----------------------
(无列名)
OM011 OC
GC012 UT
GC011 UT1
GC013 UT1
GC015 UT1

------解决方案--------------------
SQL code
WITH WorkOrder  (ProductName,EncapsulationType)
 AS(
 SELECT 'OM011', 'OC'
 UNION ALL 
 SELECT 'GC012', 'UT'
 UNION ALL 
 SELECT 'GC011', 'UT1'
 UNION ALL 
 SELECT 'GC013', 'UT1_GC013'
 UNION ALL 
 SELECT 'GC015', 'UT1_GC015'
 )
 select ProductName,CASE WHEN CHARINDEX('_',EncapsulationType,0)=0 THEN EncapsulationType 
 WHEN CHARINDEX('_',EncapsulationType,0)>0 THEN SUBSTRING(EncapsulationType,0,4) END EncapsulationType
 from WorkOrder
 /*
 ProductName EncapsulationType
 ----------- -----------------
 OM011       OC
 GC012       UT
 GC011       UT1
 GC013       UT1
 GC015       UT1
 
 (5 行受影响)
 
 
 */

------解决方案--------------------
探讨

不行哎

引用:
SQL code
select ProductName,stuff(EncapsulationType,patindex('_',EncapsulationType),len(EncapsulationType),'')EncapsulationType from WorkOrder