Can I create view with parameter in MySQL?

Question

I have a view like this:

CREATE VIEW MyView AS
   SELECT Column FROM Table WHERE Value = 2;

I'd like to make it more generic, it means to change 2 into a variable. I tried this:

CREATE VIEW MyView AS
   SELECT Column FROM Table WHERE Value = @MyVariable;

But mysql doesn't allow this.

I found an ugly workaround:

CREATE FUNCTION GetMyVariable() RETURNS INTEGER DETERMINISTIC NO SQL
BEGIN RETURN @MyVariable; END|
And then view is:
CREATE VIEW MyView AS
   SELECT Column FROM Table WHERE Value = GetMyVariable();

But it looks really crappy, and the usage is also crappy - I have to set the @MyVariable before each usage of the view.

Is there a solution, that I could use like this:

SELECT Column FROM MyView(2) WHERE (...)

The concrete situation is as follows: I have a table storing informations about denied request:

CREATE TABLE Denial
(
    Id INTEGER UNSIGNED AUTO_INCREMENT,
        PRIMARY KEY(Id),
    DateTime DATETIME NOT NULL,
    FeatureId MEDIUMINT UNSIGNED NOT NULL,
        FOREIGN KEY (FeatureId)
            REFERENCES Feature (Id)
            ON UPDATE CASCADE ON DELETE RESTRICT,
    UserHostId MEDIUMINT UNSIGNED NOT NULL,
        FOREIGN KEY (UserHostId)
            REFERENCES UserHost (Id)
            ON UPDATE CASCADE ON DELETE RESTRICT,
    Multiplicity MEDIUMINT UNSIGNED NOT NULL DEFAULT 1,
    UNIQUE INDEX DenialIndex (FeatureId, DateTime, UserHostId)
) ENGINE = InnoDB;

Multiplicity is number of identical requests recorded in the same second. I want to display a list of denials, but sometimes, when application gets denied, it retries couple times just to make sure. So usually, when the same user gets denial 3 times on the same feature in couple seconds it is actually one denial. If we'd have one more resource, to fulfill this request, next two denials would not happen. So we want to group the denials in report allowing user to specify the timespan in wich denials should be grouped. E.g. if we have denials (for user 1 on feature 1) in timestamps: 1,2,24,26,27,45 and user wants to group denials that are closer to each other than 4 sec, he should get something like this: 1 (x2), 24 (x3), 45 (x1). We can assume, that spaces between real denials are much bigger than between duplications. I solved the problem in following way:

CREATE FUNCTION GetDenialMergingTime()
    RETURNS INTEGER UNSIGNED
    DETERMINISTIC NO SQL
BEGIN
    IF ISNULL(@DenialMergingTime) THEN
        RETURN 0;
    ELSE
        RETURN @DenialMergingTime;
    END IF;
END|

CREATE VIEW MergedDenialsViewHelper AS
    SELECT MIN(Second.DateTime) AS GroupTime,
        First.FeatureId,
        First.UserHostId,
        SUM(Second.Multiplicity) AS MultiplicitySum
    FROM Denial AS First 
        JOIN Denial AS Second 
            ON First.FeatureId = Second.FeatureId
                AND First.UserHostId = Second.UserHostId
                AND First.DateTime >= Second.DateTime
                AND First.DateTime - Second.DateTime < GetDenialMergingTime()
    GROUP BY First.DateTime, First.FeatureId, First.UserHostId, First.Licenses;

CREATE VIEW MergedDenials AS
    SELECT GroupTime, 
        FeatureId,
        UserHostId, 
        MAX(MultiplicitySum) AS MultiplicitySum
    FROM MergedDenialsViewHelper
    GROUP BY GroupTime, FeatureId, UserHostId;

Then to show denials from user 1 and 2 on features 3 and 4 merged every 5 seconds all you have to do is:

SET @DenialMergingTime := 5;
SELECT GroupTime, FeatureId, UserHostId, MultiplicitySum FROM MergedDenials WHERE UserHostId IN (1, 2) AND FeatureId IN (3, 4);

I use view, becuose in it it's easy to filter data and to use it explicite in jQuery grid, automatically order, limit number of records and so on.

But it's just an ugly workaround. Is there a propper way to do this?

Answer 1

CREATE VIEW MyView AS
   SELECT Column, Value FROM Table;


SELECT Column FROM MyView WHERE Value = 1;

Is the proper solution in MySQL, some other SQLs let you define Views more exactly.

Note: Unless the View is very complicated, MySQL will optimize this just fine.