Class Random

Namespace

YndigoBlue.Velocity.Functions

Assembly

YndigoBlue.Velocity.dll

Represents the RANDOM mathematical function that generates a random number.

public class Random : Function, ICheckItem, IDefaultItem, IFilterItem, IElement

Inheritance

object

Function

Random

Implements

ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

When called with no arguments, RANDOM returns a pseudo-random floating-point value in [0, 1). When called with two arguments (lower, upper), it returns a random value within that range.

Database-specific SQL varies: SQL Server and MySQL use RAND(), PostgreSQL uses RANDOM(), Oracle uses DBMS_RANDOM.VALUE, SQLite uses RANDOM(), and Teradata uses RANDOM(lower, upper). Velocity selects the appropriate form automatically.

RANDOM is not cryptographically secure and should not be used for security-sensitive operations.

Examples

Select ten random articles from a content table:

var schema = manager.LoadSchema("content");
var articles = schema["articles"];

var query = new Query()
    .Select([ articles["id"], articles["title"] ])
    .From(articles)
    .OrderBy(new Expression("rnd", new Random()))
    .Limit(10);

var results = manager.Retrieve(query);

Generate a random integer within a hard-coded inclusive range using the integer literal constructor:

// Generates a random integer between 1 and 100 (inclusive)
var expr = new Expression("roll", new Random(1, 100));

var query = new Query().Select([ expr ]);
var results = manager.Retrieve(query);

Use the column + column constructor to generate a random value within per-row bounds stored in columns:

var schema = manager.LoadSchema("games");
var loot = schema["loot_table"];
Column minColumn = loot["min_roll"];
Column maxColumn = loot["max_roll"];

var query = new Query()
    .Select([ loot["item_id"], new Expression("roll", new Random(minColumn, maxColumn)) ])
    .From(loot);

var results = manager.Retrieve(query);

Mix a literal lower bound with a column upper bound, or a column lower bound with a literal upper bound:

var schema = manager.LoadSchema("games");
var loot = schema["loot_table"];
Column maxColumn = loot["max_roll"];
Column minColumn = loot["min_roll"];

// Fixed floor of 1.0, variable ceiling from column
var exprA = new Expression("roll_a", new Random(1.0, maxColumn));

// Variable floor from column, fixed ceiling of 100.0
var exprB = new Expression("roll_b", new Random(minColumn, 100.0));

Constructors

Random()

Initializes a new instance of RANDOM with no arguments, generating a value between 0 and 1.

Random(IEnumerable<IElement>)

Initializes a new instance of RANDOM for multiple elements.

Random(double, Column)

Initializes a new instance of RANDOM with a double lower bound and an upper bound column.

Random(int, int)

Initializes a new instance of RANDOM with integer lower and upper bound literals.

Random(IElement)

Initializes a new instance of RANDOM for a single element.

Random(Column, double)

Initializes a new instance of RANDOM with a lower bound column and a double upper bound.

Random(Column, Column)

Initializes a new instance of RANDOM with both lower and upper bound columns.