将具有NULL值的列添加到临时表

Question

I am trying to create a temp table with values from an existing table. I would like the temp table to have an additional column (phone), which does not exist from the permanent table. All values in this column should be NULL. Not sure how to do, but here is my existing query:

SELECT DISTINCT UserName, FirstName, LastName INTO ##TempTable 
FROM (
      SELECT DISTINCT Username, FirstName, LastName 
          FROM PermanentTable
)  data 

Answer 1

You need to give the column a value, but you don't need a subquery:

SELECT DISTINCT UserName, FirstName, LastName, NULL as phone
INTO ##TempTable 
FROM PermanentTable;

In SQL Server, the default type for NULL is an int. It is more reasonable to store a phone number as a string, so this is perhaps better:

SELECT DISTINCT UserName, FirstName, LastName,
       CAST(NULL as VARCHAR(255)) as phone
INTO ##TempTable 
FROM PermanentTable;

Answer 2

Just add the name of column that you will insert into TempTable and in inner select just select NULL

something like this

SELECT DISTINCT UserName, FirstName, LastName, Phone INTO ##TempTable 
FROM (
  SELECT DISTINCT Username, FirstName, LastName, NULL
      FROM PermanentTable
 )  data 

Answer 3

Rewrite the query as -

CREATE TABLE ##TempTable(UserName datatype, FirstName datatype, LastName datatype,Phone datatype)
INSERT INTO INTO ##TempTable (UserName, FirstName, LastName,Phone )
SELECT DISTINCT UserName, FirstName, LastName,NULL 
FROM (
      SELECT DISTINCT Username, FirstName, LastName 
          FROM PermanentTable
)  data