SELECT from nothing?

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

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.

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.

For ClickHouse, the nothing is system.one

SELECT 1 FROM system.one

In Firebird, you can do this:

select "Hello world" from RDB$DATABASE;

RDB$DATABASE is a special table that always has one row.

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');