使用select为查询结果添加行

Question

Is it possible to extend query results with literals like this?

select name from users
union
select name from ('JASON');

or

select age, name from users
union
select age, name from (25,'Betty');

so it returns all the names in the table plus 'JASON', or (25,'Betty').

Answer 1

You use it like this:

SELECT  age, name
FROM    users
UNION
SELECT  25 AS age, 'Betty' AS name

Use UNION ALL to allow duplicates: if there is a 25-years old Betty among your users, the second query will not select her again with mere UNION .

Answer 2

In SQL Server, you would say:

Select name from users
UNION [ALL]
SELECT 'JASON'

In Oracle, you would say

Select name from user
UNION [ALL]
Select 'JASON' from DUAL

Answer 3

is it possible to extend query results with literals like this?

Yes.

Select Name
From Customers
UNION ALL
Select 'Jason'

• Use UNION to add Jason if it isn't already in the result set.
• Use UNION ALL to add Jason whether or not he's already in the result set.