Is it possible to have a default parameter for a mysql stored procedure?

sql

stored-procedures

default-parameters

mysql

byNikita Barsukov·Oct 28, 2024

To simulate default parameters in MySQL stored procedures, use NULL checks and assign default values conditionally:

CREATE PROCEDURE MyProcedure(IN param1 INT, IN param2 INT)
BEGIN
  SET param1 = IFNULL(param1, 5); -- Insert favorite number 5 if param1 is NULL
  SET param2 = IFNULL(param2, 10); -- Inserts 10 if param2 is NULL, cause why not?

  -- Continue with your procedure logic
END;

To trigger default values, pass NULL when calling the procedure:

CALL MyProcedure(NULL, NULL); -- param1 = 5 (your new lucky number!), param2 = 10 (double the fun!)
CALL MyProcedure(20, NULL);  -- param1 = 20 (double the double fun?), param2 = 10 (still double fun!)

Increase flexibility and maintainability in your stored procedures using this handy trick.

Digging deeper: More ways to simulate defaults

MySQL stored procedures do not natively support default parameters, but as developers, we know how to find our way around their restrictions! Let's examine how we can achieve default-like behavior through a few different strategies.

Using conditional logic

You can set default values within stored procedures by using IF or CASE statements to check for NULL or empty string values. This makes your code clear about your intentions, but be careful as it can clutter your stored procedures.

Creating multiple versions of procedures

Creating overloaded versions of a procedure with different parameter lists can simulate default parameters. These different versions call a central, baseline procedure. It's like having a superhero team, with each member having a particular superpower (AKA parameter configuration) to handle different situations!

Resorting to wrapper functions

💡 Another approach is to use wrapper functions that set the defaults and call the stored procedure. This helps in decoupling and allows your procedure definition to remain clean.

Implementation details: Making defaults work

Let's dig into how to practically implement these concepts.

Using conditionals to check parameters

CREATE PROCEDURE MyProcedure(IN param1 INT, IN param2 INT)
BEGIN
  SET param1 = IF(param1 IS NULL, 5, param1); -- Five makes everything jive, if param1 isn't alive!
  SET param2 = IF(param2 IS NULL or param2 = '', 10, param2); -- If param2 is a ghost or a mystery, it becomes 10 in history!

  -- Continue with your procedure logic
END;

Creating overloaded procedures

CREATE PROCEDURE MyProcedure(IN param1 INT)
BEGIN
  CALL MyProcedure(param1, 10); -- Keep calm and carry on with ten, even when param2 takes a zen!
END;

CREATE PROCEDURE MyProcedure(IN param1 INT, IN param2 INT)
BEGIN
  -- Proceed with your procedure logic, as before
END;

Deploying wrapper functions

CREATE FUNCTION ApplyDefaults(param1 INT)
RETURNS VARCHAR(255)
BEGIN
  -- Call the procedure with the right defaults, if necessary
  RETURN CALL MyProcedure(IFNULL(param1, 5), 10); -- hero function to the rescue, setting defaults anew!
END;