sql server合并两个具有不同结构的表

Question

I have a situation where in I have to combine two tables without losing any data. The two tables have different structures. Following is the structures of my tables

TABLE A 
ID_NO INT,
Ship_Date DATE,
Status varchar(10),
total decimal(12,2)

TABLE B
ID_NO INT,
Status varchar(10),
total decimal(12,2)

I tried using UNION ALL by including a dummy column in TABLE B as follows

TABLE B
ID_NO INT,
'',
Status varchar(10),
total decimal(12,2)

but in the result set i get 1900-01-01 as Ship_Date instead of ''. How to eliminate this?

Answer 1

Use a NULL value instead of an empty string. If you don't mind the Ship_Date result as a string, then you can wrap the UNION in another select statement.

SELECT U._ID_NO, 
       CASE WHEN U.Ship_Date IS NULL 
               THEN ''
               ELSE CONVERT(NVARCHAR(50), U.Ship_Date,101) END AS Ship_Date,
       U.Status, 
       U.total 
FROM
(
  SELECT A.ID_NO, A.Ship_Date, A.Status, A.total 
  FROM TableA

  UNION ALL

  SELECT B.ID_NO, NULL AS Ship_Date, B.Status, B.total 
  FROM TableB
) AS U

Answer 2

Ship_Date is a date datatype, why not use NULL as a dummy placeholder instead?

TABLE B
ID_NO INT,
NULL,
Status varchar(10),
total decimal(12,2)

Answer 3

You're getting 1900-01-01 because that column type is DATETIME. Use NULL instead of '' if you want it to be "empty".

Try:

select 
    ID_NO,
    case
        when Ship_Date is NULL then ''
       else Ship_Date
    end as Ship_Date,
    Status,
    total
from
(
    select
        ID_NO,
        Ship_Date,
        Status,
        total
    from
        table_a

    union all

    select
        ID_NO,
        NULL as Ship_Date,
        Status,
        total
    from
        table_b 
) combined