更改表合并列T-SQL

Question

I need to alter the physical structure of a table.

Combine 2 columns into a single column for the entire table.

Eg

ID  Code  Extension
1   012   8067978

Should be

ID  Num
1   0128067978

Answer 1

You can just add them together in the select statement:

SELECT Column1 + Column2 AS 'CombinedColumn' FROM TABLE

To Permanently Add them together:

Step 1. Add Column :

   ALTER TABLE YOUR_TABLE
     ADD COLUMN Combined_Column_Name VARCHAR(15) NULL

Step 2. Combine fields

   UPDATE YOUR_TABLE
     SET Combined_Column_Name = Column1 + Column2

If you wanted to keep the table intact you could just access the table information through a view .

CREATE VIEW View_To_Access_Table
AS
   SELECT t.Column1, t.Column2, etc....
           t.CombinedColumn1 + t.CombinedColumn2 AS 'CombinedColumnName'
   FROM YOUR_TABLE t

You could also create a computed column if you didn't want to create a view:

ALTER TABLE YOUR_TABLE
  ADD COLUMN CombinedColumn AS Column1 + Column2

Answer 2

ALTER TABLE DataTable ADD FullNumber VARCHAR(15) NULL
GO

UPDATE DataTable  SET FullNumber = ISNULL(Column1, '') + ISNULL(Column2, '')
GO

-- you may have FullNumber as NOT NULL, if the number is mandatory and not null for every record
ALTER TABLE DataTable ALTER COLUMN FullNumber VARCHAR(15) NOT NULL

First step creates the column and the second makes the concatenation of strings, also taking care of null values, if any.

Before dropping old columns, you should consider their usage. If you need any of the numbers in some reports, it is harder to split the string than actually having the value stored. However, this also implies redundancy (more space, possible consistency problems).

Answer 3

You can first combine the column into a single column then perform following steps:-

update table Column1 = ISNULL(Column1, '') + ISNULL(Column2, '')

rename the column and drop the extra column from table. make sure that the column have datatype as varchar.