Class Count

Namespace

YndigoBlue.Velocity.Functions

Assembly

YndigoBlue.Velocity.dll

Represents the COUNT aggregate function that returns the number of rows or non-null values.

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

Inheritance

object

Function

Count

Implements

ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

The COUNT function counts rows in a group. When used with a column, it counts non-null values. When used without a column (COUNT(*)), it counts all rows including those with null values. This function is commonly used with GROUP BY to count items per group.

Examples

Count the number of orders placed by each customer:

var schema = manager.LoadSchema("sales");
var orders = schema["orders"];

var query = new Query()
    .Select([ orders["customer_id"], new Expression("order_count", new Count(orders["id"])) ])
    .From(orders)
    .GroupBy([ orders["customer_id"] ])
    .OrderBy(orders["customer_id"]);

var results = manager.Retrieve(query);

Constructors

Count()

Initializes a new instance of COUNT(*) that counts all rows including nulls.

Count(Column)

Initializes a new instance of COUNT for a specific column, counting non-null values.