Does Oracle Allow SELECT Queries Without a FROM Clause, and If So, What's the Recommended Approach?

Can Oracle Execute SELECT Queries Without a FROM Clause?

Oracle, unlike SQL Server, does not support SELECT queries without a FROM clause. As a workaround, it is common practice to use the dual table for such operations, as seen in the example below:

Select 1,2+3, 'my dummy string' FROM DUAL

Is This Practice Recommended?

Using the dual table for fromless SELECT queries is considered good practice in Oracle. Dual is an in-memory table that employs a fast access path (FAST DUAL) when DUMMY is not selected, eliminating I/O operations.

Originally, dual consisted of two records and was used as a dummy recordset for joining. Today, it contains only one record. However, it allows for the generation of an arbitrary number of rows using the CONNECT BY clause:

SELECT level
FROM dual
CONNECT BY
        level <= 100

Other Platforms

It's worth noting that MySQL also supports the use of dual and fromless SELECT syntax.

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