只需一点字符串操作

Declare @YourTable Table ([PhoneNumber] varchar(50))
Insert Into @YourTable Values 
 ('1111111')
,('1111111name')
,('1111111ext2222name')
,('1111111ex222name')

Select * 
      ,NewValue = substring([PhoneNumber],1,len([PhoneNumber])-patindex('%[0-9]%',reverse([PhoneNumber])))
 From  @YourTable

结果

PhoneNumber         NewValue
1111111             111111
1111111name         111111
1111111ext2222name  1111111ext222
1111111ex222name    1111111ex22