How can I create a blank/hardcoded column in a sql query?

Question

I want have a query with a column that is a hardcoded value not from a table, can this be done? I need it basically as a placeholder that I am going to come back to later and fill in.

example:

SELECT
hat,
shoe,
boat,
somevalue = 0 as placeholder
FROM
objects

then I would loop through this query later and fill in the placeholder

in this example someValue is not a field in objects, I need to fake it. I am doing this in coldfusion and using two datasources to complete one query. I have tried the space() function but have been unable to get it to work.

Thanks.

Solution 1

SELECT
    hat,
    shoe,
    boat,
    0 as placeholder
FROM
    objects

And '' as placeholder for strings.

Solution 2

This should work on most databases. You can also select a blank string as your extra column like so:

Select
  Hat, Show, Boat, '' as SomeValue
From
  Objects

Solution 3

For varchars, you may need to do something like this:

select convert(varchar(25), NULL) as abc_column into xyz_table

If you try

select '' as abc_column into xyz_table

you may get errors related to truncation, or an issue with null values, once you populate.

Solution 4

The answers above are correct, and what I'd consider the "best" answers. But just to be as complete as possible, you can also do this directly in CF using queryAddColumn.

See http://www.cfquickdocs.com/cf9/#queryaddcolumn

Again, it's more efficient to do it at the database level... but it's good to be aware of as many alternatives as possible (IMO, of course) :)

View more solutions

Comments

[Leigh]

Yes, when using select...into to create a new table it is important to be more explicit about data type and capacity. Otherwise, the db will use the empty string to "guess" about the target column's properties. In the case of an empty string - it will almost certainly come up with the wrong answer.

[Leigh]

This is a repeat of the existing answers.

[Jobs]

How about for type timestamptz?