SELECT from nothing? - sql

Question

Is it possible to have a statement like
SELECT "Hello world"
WHERE 1 = 1
in SQL?
The main thing I want to know, is can I SELECT from nothing, ie not have a FROM clause.

Answer 1

It's not consistent across vendors - Oracle, MySQL, and DB2 support dual:
SELECT 'Hello world'
FROM DUAL
...while SQL Server, PostgreSQL, and SQLite don't require the FROM DUAL:
SELECT 'Hello world'
MySQL does support both ways.

Answer 2

Try this.
Single:
SELECT * FROM (VALUES ('Hello world')) t1 (col1) WHERE 1 = 1
Multi:
SELECT * FROM (VALUES ('Hello world'),('Hello world'),('Hello world')) t1 (col1) WHERE 1 = 1
more detail here : http://modern-sql.com/use-case/select-without-from

Answer 3

In Oracle:
SELECT 'Hello world' FROM dual
Dual equivalent in SQL Server:
SELECT 'Hello world'

Answer 4

Here is the most complete list of database support of dual from https://blog.jooq.org/tag/dual-table/:
In many other RDBMS, there is no need for dummy tables, as you can
issue statements like these:
SELECT 1;
SELECT 1 + 1;
SELECT SQRT(2);
These are the RDBMS, where the above is generally possible:
H2
MySQL
Ingres
Postgres
SQLite
SQL Server
Sybase ASE
In other RDBMS, dummy tables are required, like in Oracle. Hence,
you’ll need to write things like these:
SELECT 1 FROM DUAL;
SELECT 1 + 1 FROM DUAL;
SELECT SQRT(2) FROM DUAL;
These are the RDBMS and their respective dummy tables:
DB2: SYSIBM.DUAL
Derby: SYSIBM.SYSDUMMY1
H2: Optionally supports DUAL
HSQLDB: INFORMATION_SCHEMA.SYSTEM_USERS
MySQL: Optionally supports DUAL
Oracle: DUAL
Sybase SQL Anywhere: SYS.DUMMY
Ingres has no DUAL, but would actually need it as in Ingres you cannot
have a WHERE, GROUP BY or HAVING clause without a FROM clause.

Answer 5

In SQL Server type:
Select 'Your Text'
There is no need for the FROM or WHERE clause.

Answer 6

You can. I'm using the following lines in a StackExchange Data Explorer query:
SELECT
(SELECT COUNT(*) FROM VotesOnPosts WHERE VoteTypeName = 'UpMod' AND UserId = #UserID AND PostTypeId = 2) AS TotalUpVotes,
(SELECT COUNT(*) FROM Answers WHERE UserId = #UserID) AS TotalAnswers
The Data Exchange uses Transact-SQL (the SQL Server proprietary extensions to SQL).
You can try it yourself by running a query like:
SELECT 'Hello world'

Answer 7

There is another possibility - standalone VALUES():
VALUES ('Hello World');
Output:
column1
Hello World
It is useful when you need to specify multiple values in compact way:
VALUES (1, 'a'), (2, 'b'), (3, 'c');
Output:
column1 column2
1 a
2 b
3 c
DBFiddle Demo
This syntax is supported by SQLite/PostgreSQL/DB LUW/MariaDB 10.3.

Answer 8

In Firebird, you can do this:
select "Hello world" from RDB$DATABASE;
RDB$DATABASE is a special table that always has one row.

Answer 9

I think it is not possible. Theoretically: select performs two sorts of things:
narrow/broaden the set (set-theory);
mapping the result.
The first one can be seen as a horizontal diminishing opposed to the where-clause which can be seen as a vertical diminishing. On the other hand, a join can augment the set horizontally where a union can augment the set vertically.
augmentation diminishing
horizontal join/select select
vertical union where/inner-join
The second one is a mapping. A mapping, is more a converter. In SQL it takes some fields and returns zero or more fields. In the select, you can use some aggregate functions like, sum, avg etc. Or take all the columnvalues an convert them to string. In C# linq, we say that a select accepts an object of type T and returns an object of type U.
I think the confusion comes by the fact that you can do: select 'howdy' from <table_name>. This feature is the mapping, the converter part of the select. You are not printing something, but converting! In your example:
SELECT "
WHERE 1 = 1
you are converting nothing/null into "Hello world" and you narrow the set of nothing / no table into one row, which, imho make no sense at all.
You may notice that, if you don't constrain the number of columns, "Hello world" is printed for each available row in the table. I hope, you understand why by now. Your select takes nothing from the available columns and creates one column with the text: "Hello world".
So, my answer is NO. You can't just leave out the from-clause because the select always needs table-columns to perform on.

Answer 10

In Standard SQL, no. A WHERE clause implies a table expression.
From the SQL-92 spec:
7.6 "where clause"
Function
Specify a table derived by the
application of a "search condition" to
the result of the preceding "from
clause".
In turn:
7.4 "from clause"
Function
Specify a table derived from one or more named tables.
A Standard way of doing it (i.e. should work on any SQL product):
SELECT DISTINCT 'Hello world' AS new_value
FROM AnyTableWithOneOrMoreRows
WHERE 1 = 1;
...assuming you want to change the WHERE clause to something more meaningful, otherwise it can be omitted.

Answer 11

For ClickHouse, the nothing is system.one
SELECT 1 FROM system.one

Answer 12

I know this is an old question but the best workaround for your question is using a dummy subquery:
SELECT 'Hello World'
FROM (SELECT name='Nothing') n
WHERE 1=1
This way you can have WHERE and any clause (like Joins or Apply, etc.) after the select statement since the dummy subquery forces the use of the FROM clause without changing the result.

Answer 13

For DB2:
`VALUES('Hello world')`
You can do multiple "rows" as well:
`VALUES('Hello world'),('Goodbye world');`
You can even use them in joins as long as the types match:
VALUES(1,'Hello world')
UNION ALL
VALUES(2,'Goodbye world');

Answer 14

I'm using firebird
First of all, create a one column table named "NoTable" like this
CREATE TABLE NOTABLE
(
NOCOLUMN INTEGER
);
INSERT INTO NOTABLE VALUES (0); -- You can put any value
now you can write this
select 'hello world' as name
from notable
you can add any column you want to be shown