从 jeft 连接查询中选择特定列，TypeORM

Question

我有一个任务来获取有关数据库中用户的关键信息。有很多left joins，查询的工作速度很慢。我试图以某种方式优化它，我决定只选择特定的字段（目前只选择记录的 id）。

这是我查询的一部分。我只需要获取属于用户的每个事件的 id，并对数据库中的每个用户执行相同的操作。理想情况下，我应该得到一组 id。

我试图建立一个子查询，但找不到一些解释的例子。官方文档中的一个例子对我来说还不够。

当我运行它时，我收到错误

syntax error at or near "SELECT"
QueryFailedError: syntax error at or near "SELECT"

this.createQueryBuilder('profile')
            .leftJoinAndSelect('profile.avatarPhoto', 'avatarPhoto')
            .leftJoinAndSelect('profile.coverPhoto', 'coverPhoto')
            .leftJoinAndSelect('profile.primaryCountry', 'country')
            .leftJoinAndSelect('profile.primaryCity', 'city')
            .leftJoinAndSelect('profile.images', 'image')
            .leftJoinAndSelect('profile.practicedSports', 'practicedSport')
            .leftJoinAndSelect(
                (subQuery) =>
                    subQuery
                        .subQuery()
                        .createQueryBuilder()
                        .select(['id'])
                        .leftJoin('user', 'user')
                        .from(SportEvent, 'event'),
                'event',
                'event.user.id = profile.id',
            )
            // .leftJoinAndSelect('profile.sportServices', 'service')
            // .leftJoinAndSelect('profile.lessons', 'lesson')
            // .leftJoinAndSelect('profile.activityRequests', 'request')
            .leftJoin('profile.userAuth', 'auth')
            .where('auth.registered = true')
            .andWhere('auth.blocked = false')
            .take(params.pageSize)
            .skip(itemsNumber)
            .getMany()

这是生成的SQL代码

SELECT DISTINCT "distinctAlias"."profile_id" as "ids_profile_id" 
FROM (SELECT "profile"."id" AS "profile_id", "profile"."email" AS "profile_email", 
"profile"."first_name" AS "profile_first_name", 
"profile"."middle_name" AS "profile_middle_name", 
"profile"."last_name" AS "profile_last_name", 
"profile"."about_user" AS "profile_about_user", 
"profile"."interests" AS "profile_interests", 
"profile"."birthday" AS "profile_birthday", 
"profile"."gender" AS "profile_gender", 
"profile"."sport_level" AS "profile_sport_level", 
"profile"."phone_number" AS "profile_phone_number", 
"profile"."contacts" AS "profile_contacts", 
"profile"."payment_methods" AS "profile_payment_methods", 
"profile"."settings" AS "profile_settings", 
"profile"."options" AS "profile_options", 
"profile"."updated_at" AS "profile_updated_at", 
"profile"."created_at" AS "profile_created_at", 
"profile"."avatar_photo_id" AS "profile_avatar_photo_id", 
"profile"."cover_photo_id" AS "profile_cover_photo_id", 
"profile"."cover_video_id" AS "profile_cover_video_id", 
"profile"."default_album_id" AS "profile_default_album_id", 
"profile"."primary_country_id" AS "profile_primary_country_id", 
"profile"."primary_city_id" AS "profile_primary_city_id", 
"profile"."primary_language_id" AS "profile_primary_language_id", 
"avatarPhoto"."id" AS "avatarPhoto_id", 
"avatarPhoto"."name" AS "avatarPhoto_name", 
"avatarPhoto"."image_paths" AS "avatarPhoto_image_paths", 
"avatarPhoto"."updated_at" AS "avatarPhoto_updated_at", 
"avatarPhoto"."created_at" AS "avatarPhoto_created_at", 
"avatarPhoto"."album_id" AS "avatarPhoto_album_id", 
"avatarPhoto"."user_id" AS "avatarPhoto_user_id", 
"coverPhoto"."id" AS "coverPhoto_id", 
"coverPhoto"."name" AS "coverPhoto_name", 
"coverPhoto"."image_paths" AS "coverPhoto_image_paths", 
"coverPhoto"."updated_at" AS "coverPhoto_updated_at", 
"coverPhoto"."created_at" AS "coverPhoto_created_at", 
"coverPhoto"."album_id" AS "coverPhoto_album_id", 
"coverPhoto"."user_id" AS "coverPhoto_user_id", 
"country"."id" AS "country_id", 
"country"."name" AS "country_name", 
"country"."alpha_2" AS "country_alpha_2", 
"country"."alpha_3" AS "country_alpha_3", 
"country"."calling_code" AS "country_calling_code", 
"country"."enabled" AS "country_enabled", 
"country"."top" AS "country_top", "city"."id" AS "city_id", 
"city"."name" AS "city_name", 
"city"."coordinates" AS "city_coordinates", 
"city"."top" AS "city_top", 
"city"."country_id" AS "city_country_id", 
"image"."id" AS "image_id", 
"image"."name" AS "image_name", 
"image"."image_paths" AS "image_image_paths", 
"image"."updated_at" AS "image_updated_at", 
"image"."created_at" AS "image_created_at", 
"image"."album_id" AS "image_album_id", 
"image"."user_id" AS "image_user_id", 
"practicedSport"."id" AS "practicedSport_id", 
"practicedSport"."start_date" AS "practicedSport_start_date", 
"practicedSport"."sport_id" AS "practicedSport_sport_id", 
"practicedSport"."user_id" AS "practicedSport_user_id", 
"event".* 
FROM "user_profiles" "profile" LEFT JOIN "media_images" "avatarPhoto" 
ON "avatarPhoto"."id"="profile"."avatar_photo_id"  LEFT JOIN "media_images" "coverPhoto" 
ON "coverPhoto"."id"="profile"."cover_photo_id"  LEFT JOIN "data_countries" "country" 
ON "country"."id"="profile"."primary_country_id"  LEFT JOIN "data_cities" "city" 
ON "city"."id"="profile"."primary_city_id"  LEFT JOIN "media_images" "image" 
ON "image"."user_id"="profile"."id"  LEFT JOIN "user_practiced_sports" "practicedSport" 
ON "practicedSport"."user_id"="profile"."id"  
LEFT JOIN SELECT id FROM "sport_events" "event" 
LEFT JOIN "user" "user" "event" 
ON event.user.id = "profile"."id"  
LEFT JOIN "user_auth" "auth" 
ON "auth"."profile_id"="profile"."id" 
WHERE "auth"."registered" = true 
AND auth.blocked = false) "distinctAlias" 
ORDER BY "profile_id" ASC LIMIT 15

你能解释一下我做错了什么或给我发一篇解释的文章吗？谢谢！

Answer 1

我认为不可能加入，event.user.id您应该将其分成两个 leftJoins。另请确保使用（然后通过或leftJoin(..)指定要选择的字段）而不是，因为这会自动选择所有字段。.select(..).addSelect(..)leftJoinAndSelect(..)

Answer 2

您可以使用 .leftJoin(property, alias).addSelect([alias.fieldToSelect]) 而不是 leftJoinAndSelect()

示例：假设您已在实体中编写了关系，则假设您有 table1.field1 要连接到 table2.field2。你可以做，

  const data = await this.table1Repository.createQueryBuilder("t1")
               .leftJoin('t1.relationName', 'alias')
               .addSelect(['alias.fieldYouWantToSelect']);