Class NullIf

Namespace

YndigoBlue.Velocity.Functions

Assembly

YndigoBlue.Velocity.dll

Represents the NULLIF function that returns NULL if two expressions are equal, otherwise returns the first expression.

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

Inheritance

object

Function

NullIf

Implements

ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

The NULLIF function compares two expressions and returns NULL if they are equal, otherwise it returns the first expression. This is equivalent to: CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END. NULLIF is useful for converting specific values to NULL (e.g., converting empty strings or sentinel values like -1 to NULL), preventing division by zero, or normalizing data.

Examples

Return null instead of zero to avoid division-by-zero errors:

var schema = manager.LoadSchema("finance");
var accounts = schema["accounts"];

var query = new Query()
    .Select([ accounts["id"], new Expression("safe_balance", new NullIf(accounts["balance"], 0.0)) ])
    .From(accounts);

var results = manager.Retrieve(query);

Constructors

NullIf(IElement, IElement)

Initializes a new instance of NULLIF with generic element-based arguments.

NullIf(Column, double)

Initializes a new instance of NULLIF with a column and a double literal.

NullIf(Column, int)

Initializes a new instance of NULLIF with a column and an integer literal.

NullIf(Column, string)

Initializes a new instance of NULLIF with a column and a string literal.

NullIf(Column, Column)

Initializes a new instance of NULLIF with column-based expressions.

NullIf(Expression, Expression)

Initializes a new instance of NULLIF with expression-based arguments.