Macro concept in SQL - mysql

Question

Do any database engines have the concept of a C-like macro? Here would be an example where I'd just like to make it more readable:
SELECT
SUM(Profit) AS Total,
(SELECT AVG(Profit) FROM This
WHERE Category=This.Category AND Product=This.Product
AND PARSE_DATE('%M %d%, Y', CONCAT(This.Month ' 1, ' This.Year))
BETWEEN PARSE_DATE('%M %d%, Y', CONCAT(This.Month ' 1, ' This.Year))
AND PARSE_DATE('%M %d%, Y', CONCAT(This.Month ' 1, ' This.Year))-INTERVAL 3 MONTH
FROM Tbl
I would rather have something that looks like:
#define dt PARSE_DATE('%M %d%, Y', CONCAT(This.Month ' 1, ' This.Year))
SELECT
SUM(Profit) AS Total,
(SELECT AVG(Profit) FROM This
WHERE Category=This.Category AND Product=This.Product
AND dt BETWEEN dt AND (dt-INTERVAL 3 MONTH)
FROM Tbl
Does something like that exist or commonly-used in the major DBMSs?

Answer 1

From Oracle 12, you can declare a function inside a sub-query factoring (WITH) clause:
WITH FUNCTION dt (month INT, year INT) RETURN DATE AS
BEGIN
RETURN TO_DATE(year || '-' || month || '-01', 'YYYY-MM-DD');
END;
SELECT *
FROM this
WHERE dt(this.month, this.year)
BETWEEN ADD_MONTHS(dt(this.month, this.year), -3)
AND dt(this.month, this.year);
db<>fiddle here
From Oracle 21, you can write SQL macros:
CREATE FUNCTION dt (month INT, year INT)
RETURN VARCHAR2 SQL_MACRO(SCALAR)
AS
BEGIN
RETURN 'TO_DATE(year || ''-'' || month || ''-01'', ''YYYY-MM-DD'')';
END;
/
Then would use it as:
SELECT *
FROM this
WHERE dt(this.month, this.year)
BETWEEN ADD_MONTHS(dt(this.month, this.year), -3)
AND dt(this.month, this.year);
And the query would get rewritten as:
SELECT *
FROM this
WHERE TO_DATE(this.year || '-' || this.month || '-01', 'YYYY-MM-DD')
BETWEEN ADD_MONTHS(TO_DATE(this.year || '-' || this.month || '-01', 'YYYY-MM-DD'), -3)
AND TO_DATE(this.year || '-' || this.month || '-01', 'YYYY-MM-DD');