# 使用查询引擎 API 填充

> Source: https://strapi.nodejs.cn/cms/api/query-engine/populating

🌐 Populating with the Query Engine API

查询引擎 API 的 `populate` 参数在查询中加载相关数据，支持基本填充、选择性属性、过滤嵌套关系以及通过填充片段处理多态结构。

🌐 The Query Engine API's `populate` parameter loads related data in queries, supporting basic population, selective attributes, filtering nested relations, and polymorphic structures via populate fragments.

:::caution

在大多数情况下，你不应该使用查询引擎 API，而应使用 [文档服务 API](/cms/api/document-service)。

🌐 In most cases you should not use the Query Engine API and rather use the [Document Service API](/cms/api/document-service).

仅当你确切知道自己在做什么时才使用查询引擎 API，例如，如果你想使用直接与数据库的唯一行交互的底层 API。

🌐 Only use the Query Engine API if you exactly know what you are doing, for instance if you want to use a lower-level API that directly interacts with unique rows of the database.

请记住，查询引擎 API 并不了解 Strapi 5 的最新功能，如草稿与发布、国际化、内容历史记录等，可能还有更多功能。这也意味着查询引擎 API 将无法使用 `documentId`，而将使用 `id`，这可能会在数据库层面导致未预料的后果，或者与 Strapi 5 功能存在部分或不完全兼容的情况。 

🌐 Please keep in mind that the Query Engine API is not aware of the most advanced Strapi 5 features like Draft & Publish, Internationalization, Content History, and possibly more.
This also means that the Query Engine API will not be able to use `documentId` and will use `id`, which means it could lead to unattended consequences at the database level or partial or incomplete compatibility with Strapi 5 features. 

:::

:::prerequisites

在深入了解查询引擎 API 文档之前，建议你阅读以下介绍：

🌐 Before diving deeper into the Query Engine API documentation, it is recommended that you read the following introductions:

- 关于[后端自定义介绍](/cms/backend-customization)，
- 以及 [内容 API 介绍](/cms/api/content-api)。

:::

关系和组件有一个统一的 API 来填充它们。

🌐 Relations and components have a unified API for populating them.

要填充所有根级关系，请使用 `populate: true`：

🌐 To populate all the root level relations, use `populate: true`:

```js
strapi.db.query('api::article.article').findMany({
  populate: true,
});
```

通过传递属性名称数组来选择要填充的数据：

🌐 Select which data to populate by passing an array of attribute names:

```js
strapi.db.query('api::article.article').findMany({
  populate: ['componentA', 'relationA'],
});
```

可以传递一个对象以进行更高级的用法：

🌐 An object can be passed for more advanced usage:

```js
strapi.db.query('api::article.article').findMany({
  populate: {
    componentB: true,
    dynamiczoneA: true,
    relation: someLogic || true,
  },
});
```

复杂的填充也可以通过应用 `where` 过滤器并选择或填充嵌套关系来实现：

🌐 Complex populating can also be achieved by applying `where` filters and select or populate nested relations:

```js
strapi.db.query('api::article.article').findMany({
  populate: {
    relationA: {
      where: {
        name: {
          $contains: 'Strapi',
        },
      },
    },

    repeatableComponent: {
      select: ['someAttributeName'],
      orderBy: ['someAttributeName'],
      populate: {
        componentRelationA: true,
      },
    },

    dynamiczoneA: true,
  },
});
```

在处理多态内容结构（动态区域、多态关系等）时，可以使用填充片段来更好地控制填充策略。

🌐 When dealing with polymorphic content structures (dynamic zones, polymorphic relations, etc...), it is possible to use populate fragments to have a better granularity on the populate strategy.

```js
strapi.db.query('api::article.article').findMany('api::article.article', {
  populate: {
    dynamicZone: {
      on: {
        'components.foo': {
          select: ['title'],
          where: { title: { $contains: 'strapi' } },
        },
        'components.bar': {
          select: ['name'],
        },
      },
    },

    morphAuthor: {
      on: {
        'plugin::users-permissions.user': {
          select: ['username'],
        },
        'api::author.author': {
          select: ['name'],
        },
      },
    },
  },
});
```