TypeORM select alias of column name

Setting aliases for selected column names in TypeORM is a common requirement, especially useful when handling complex queries or enhancing the readability of query results. To set aliases for column names, you can specify them when using QueryBuilder or certain query methods.

Using QueryBuilder to Set Aliases

When using QueryBuilder to construct queries, you can set aliases for specific columns via the select method. For example, suppose we have an entity named user containing the fields firstName and lastName; we can set aliases for them as follows:

typescript
import { getRepository } from "typeorm";

const userRepository = getRepository(User);

const users = await userRepository
  .createQueryBuilder("user")
  .select("user.firstName", "firstNameAlias")
  .addSelect("user.lastName", "lastNameAlias")
  .getMany();

console.log(users); // The resulting objects will contain firstNameAlias and lastNameAlias instead of firstName and lastName

In the above code, "user.firstName" is the actual column name, while "firstNameAlias" is the alias we set. This way, the properties in the resulting array will use the aliases instead of the original column names.

Setting Aliases with Query Methods

In some simple queries, such as when using the find method, you can also set aliases by using the select parameter in the options. For example:

typescript
import { getRepository } from "typeorm";

const userRepository = getRepository(User);

const users = await userRepository.find({
  select: {
    firstName: "firstNameAlias",
    lastName: "lastNameAlias"
  }
});

console.log(users); // The results will also contain columns represented by the aliases

Summary

Using aliases helps handle query results more flexibly, making the results more intuitive and understandable. In TypeORM, whether using QueryBuilder or simple query methods, you can set column aliases in a similar way to meet different query requirements and data processing scenarios.