To not publicly disclose our amount of invoices, we want to add random value between 2 ids.
Instead of [1,2,3] we want something like [69,98,179]
UUID is not an option in that project, unfortunately.
Using Mysql 5.7, 8, or MariaDb get the same results.
Here is the approach is taken:
Consider a simple table invoices as follows:
CREATE TABLE `invoices` (
`id` bigint(20) NOT NULL,
`name` varchar(255) DEFAULT NULL,
`created_at` datetime NOT NULL,
`updated_at` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=42 DEFAULT CHARSET=utf8mb4;
The function to get random values:
DROP FUNCTION IF EXISTS random_integer;
CREATE FUNCTION random_integer(value_minimum INT, value_maximum INT)
RETURNS INT
LANGUAGE SQL
NOT DETERMINISTIC
RETURN FLOOR(value_minimum + RAND() * (value_maximum - value_minimum + 1));
The function to get the next id:
DROP FUNCTION IF EXISTS next_invoice_id_val;
DELIMITER //
CREATE FUNCTION next_invoice_id_val ()
RETURNS BIGINT(8)
LANGUAGE SQL
NOT DETERMINISTIC
BEGIN
DECLARE lastId BIGINT(8) DEFAULT 1;
DECLARE randId BIGINT(8) DEFAULT 1;
DECLARE newId BIGINT(8) DEFAULT 1;
DECLARE nextId BIGINT(8) DEFAULT 1;
SELECT (SELECT MAX(`id`) FROM `invoices`) INTO lastId;
SELECT (SELECT random_integer(1,10)) INTO randId;
SELECT ( lastId + randId ) INTO nextId;
IF lastId IS NULL
THEN
SET newId = randId;
ELSE
SET newId = nextId;
END IF;
RETURN newId;
END //
DELIMITER ;
SELECT next_invoice_id_val();
and the trigger:
DROP TRIGGER IF EXISTS next_invoice_id_val_trigger;
DELIMITER //
CREATE TRIGGER next_invoice_id_val_trigger
BEFORE INSERT
ON invoices FOR EACH ROW
BEGIN
SET NEW.id = next_invoice_id_val();
END//
DELIMITER ;
That work like a charm, now if we want to generalize the behaviour to all tables.
We need a procedure to execute the query on any specific tables:
DROP PROCEDURE IF EXISTS last_id;
DELIMITER //
CREATE PROCEDURE last_id (IN tableName VARCHAR(50), OUT lastId BIGINT(8))
COMMENT 'Gets the last id value'
LANGUAGE SQL
NOT DETERMINISTIC
READS SQL DATA
BEGIN
SET @s := CONCAT('SELECT MAX(`id`) FROM `',tableName,'`');
PREPARE QUERY FROM @s;
EXECUTE QUERY;
DEALLOCATE PREPARE QUERY;
END //
DELIMITER ;
CALL last_id('invoices', @nextInvoiceId);
SELECT @nextInvoiceId;
The procedure for the next id value:
DROP PROCEDURE IF EXISTS next_id_val;
DELIMITER //
CREATE PROCEDURE next_id_val (IN tableName VARCHAR(50), OUT nextId BIGINT(8))
COMMENT 'Give the Next Id value + a random value'
LANGUAGE SQL
NOT DETERMINISTIC
READS SQL DATA
BEGIN
DECLARE randId BIGINT(8) DEFAULT 1;
SELECT (SELECT random_integer(1,10)) INTO randId;
CALL last_id(tableName, @currentId);
IF @currentId IS NULL
THEN
SET nextId = randId;
ELSE
SELECT ( @currentId + randId ) INTO nextId;
END IF;
END //
DELIMITER ;
CALL next_id_val('invoices', @nextInvoiceId);
SELECT @nextInvoiceId;
and the trigger:
# Call the procedure from a trigger
DROP TRIGGER IF EXISTS next_invoice_id_val_trigger;
DELIMITER //
CREATE TRIGGER next_invoice_id_val_trigger
BEFORE INSERT
ON invoices FOR EACH ROW
BEGIN
CALL next_id_val('invoices', @nextInvoiceId);
SET NEW.id = @nextInvoiceId;
END//
DELIMITER ;
and we get => Dynamic SQL is not allowed in stored function or trigger
I've read that storing in a temporary table might be a workaround, but as all posts have between 5 to 10 years old, I think we might have a better solution for such a straightforward case.
