Class Column

Namespace: YndigoBlue.Velocity.Model

Assembly: YndigoBlue.Velocity.dll

Represents a column in a database table.

public class Column : ISelectItem, IElement, ICheckItem, IGroupItem, IEquatable<Column>, IEquatable<string>, IComparable<Column>

Inheritance: object

Column

Implements: ISelectItem

IElement

ICheckItem

IGroupItem

IEquatable<Column>

IEquatable<string>

IComparable<Column>

Examples

Adding columns to a table:

Table usersTable = schema.CreateTable("users");

// Auto-incrementing primary key
usersTable.AddColumn("user_id", DataType.Long, autoGenerate: true, notNull: true);

// Required text column with size limit
usersTable.AddColumn("username", DataType.VarChar, size: 100, notNull: true);

// Optional text column
usersTable.AddColumn("email", DataType.VarChar, size: 200);

// Numeric columns with precision and scale
usersTable.AddColumn("balance", DataType.Decimal, precision: 10, scale: 2);

// Integer column
usersTable.AddColumn("age", DataType.Integer);

// Date/time columns
usersTable.AddColumn("created_at", DataType.DateTime);
usersTable.AddColumn("birth_date", DataType.Date);

// Boolean column
usersTable.AddColumn("is_active", DataType.Boolean);

// Binary data column
usersTable.AddColumn("profile_image", DataType.VarBinary, size: 1048576); // 1MB

Referencing columns in queries:

Table usersTable = schema["users"];

// Access column by name
Column usernameColumn = usersTable["username"];
Column emailColumn = usersTable["email"];

Query query = new Query();
query.AddFromItem(usersTable);
query.AddSelectItem(usernameColumn);
query.AddSelectItem(emailColumn);
query.AddFilter(usersTable["age"], ConditionalType.GreaterThan, 18);
query.AddOrderClause(new OrderClause(usernameColumn, OrderClauseType.Ascending));

Using columns in constraints:

// Primary key
usersTable.AddPrimaryKey("pk_users", usersTable["user_id"]);

// Unique constraint
usersTable.AddUnique("uk_email", usersTable["email"]);

// Foreign key
ordersTable.AddForeignKey(
    "fk_orders_users",
    ordersTable["user_id"],
    usersTable["user_id"]
);

// Check constraint
usersTable.AddCheck("ck_age", usersTable["age"], CheckOperator.GreaterThanOrEquals, 0);

Remarks

Columns define the structure of data within a table, specifying the data type, size constraints, nullability, and whether values are auto-generated.

Columns are created using AddColumn(string, DataType, bool, bool, int, byte, byte) or CreateColumn(string, DataType, bool, bool, int, byte, byte) methods, and can be referenced in queries, constraints, and indexes.

Fields

_autoGenerate

_dataType

_fromItem

_name

_notNull

_precision

_scale

_size

Properties

AutoGenerate

CheckConstraintType: Gets the type of check constraint element.

ColumnUpdate

DataType: Gets the data type of the values returned by this select item.

ExistingRowType

ExistingRowValue

FromItem

Name: Gets the name of the select item as it appears in the result set.

NotNull

Precision: Gets the precision for numeric data types.

Scale: Gets the scale for numeric data types.

SchemaName: Gets the name of the schema that contains the table this column belongs to.

SchemaUpdate

Size: Gets the maximum size for string or binary data types.

Methods

CompareTo(Column): Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

Equals(string): Indicates whether the current object is equal to another object of the same type.

Equals(Column): Indicates whether the current object is equal to another object of the same type.

IsEqual(ICheckItem): Determines whether this check item is equal to another check item.

ModifyDataType(DataType)

ModifyNotNull(bool)

ModifyPrecisionScale(byte, byte)

ModifySize(int)

ReType(DataType, int)