How Can I Retrieve the First N Positive Integers Using Only a SQL SELECT Statement?

Retrieving the First N Positive Integers Using SQL SELECT

The requirement to extract the first N positive integers using solely a standard SQL SELECT statement arises occasionally. However, ascertaining the feasibility of such a request without a pre-populated count table is crucial.

Standard SQL Approach

In the realm of standard SQL, directly retrieving a sequential series of positive integers without a count table is unachievable.

MySQL-Specific Solutions

MySQL lacks a native function to generate sequential numbers, but it allows for the creation of dummy rowsets to circumvent this limitation. Consider the following examples from various database management systems:

• Oracle:

SELECT  level
FROM    dual
CONNECT BY
        level <= 10

• SQL Server:

WITH    q AS
        (
        SELECT  1 AS num
        UNION ALL
        SELECT  num + 1
        FROM    q
        WHERE   num < 10
        )
SELECT  *
FROM    q

• PostgreSQL:

SELECT  num
FROM    generate_series(1, 10) num

MySQL Limitations

Unfortunately, MySQL does not provide a comparable function, which can be seen as a drawback. A workaround can be to employ a user-defined procedure to fill a temporary table with the desired number of rows, facilitating subsequent retrieval. For instance:

CREATE TABLE filler (
        id INT NOT NULL PRIMARY KEY AUTO_INCREMENT
) ENGINE=Memory;

CREATE PROCEDURE prc_filler(cnt INT)
BEGIN
        DECLARE _cnt INT;
        SET _cnt = 1;
        WHILE _cnt <= cnt DO
                INSERT
                INTO    filler
                SELECT  _cnt;
                SET _cnt = _cnt + 1;
        END WHILE;
END
$$

CALL prc_filler(10);
SELECT  * FROM filler;

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