#TIL 10 - Add User Define Function to TypeORM entity

What

Map a SQL user-defined function (UDF) result to a TypeORM entity field using addSelect.

Why

TypeORM has no first-class UDF support — it only knows about table columns. Adding a virtual @Column with insert: false and aliasing the UDF as tableName_columnName in QueryBuilder lets you read computed values as entity properties.

How

1. Add virtual column to entity:

@Column('int', { insert: false, readonly: true })
public qty: number;

2. Select UDF in QueryBuilder:

repository
  .createQueryBuilder("user")
  .addSelect("dbo.udfFindTotalQty(user.id)", "user_qty")
  .getManyAndCount();

Note: Alias follows tableName_columnName convention (e.g., user_qty).