连接 [SQL]

SQL 中的连接子句用于根据两个或多个表之间的相关列来合并它们。Drizzle ORM 的连接语法在 SQL 相似性和类型安全性之间取得了平衡。

连接类型

Drizzle ORM 提供适用于 INNER JOIN [LATERAL]、FULL JOIN、LEFT JOIN [LATERAL]、RIGHT JOIN、CROSS JOIN [LATERAL] 的 API。让我们快速浏览一下基于下表结构的示例：

export const users = pgTable('users', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
});

export const pets = pgTable('pets', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
  ownerId: integer('owner_id').notNull().references(() => users.id),
})

左连接

const result = await db.select().from(users).leftJoin(pets, eq(users.id, pets.ownerId))

select ... from "users" left join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    pets: {
        id: number;
        name: string;
        ownerId: number;
    } | null;
}[];

左横向连接

const subquery = db.select().from(pets).where(gte(users.age, 16)).as('userPets')
const result = await db.select().from(users).leftJoinLateral(subquery, sql`true`)

select ... from "users" left join lateral (select ... from "pets" where "users"."age" >= 16) "userPets" on true

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    userPets: {
        id: number;
        name: string;
        ownerId: number;
    } | null;
}[];

右连接

const result = await db.select().from(users).rightJoin(pets, eq(users.id, pets.ownerId))

select ... from "users" right join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
    user: {
        id: number;
        name: string;
    } | null;
    pets: {
        id: number;
        name: string;
        ownerId: number;
    };
}[];

内部连接

const result = await db.select().from(users).innerJoin(pets, eq(users.id, pets.ownerId))

select ... from "users" inner join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    pets: {
        id: number;
        name: string;
        ownerId: number;
    };
}[];

内连接横向

const subquery = db.select().from(pets).where(gte(users.age, 16)).as('userPets')
const result = await db.select().from(users).innerJoinLateral(subquery, sql`true`)

select ... from "users" inner join lateral (select ... from "pets" where "users"."age" >= 16) "userPets" on true

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    userPets: {
        id: number;
        name: string;
        ownerId: number;
    };
}[];

全连接

const result = await db.select().from(users).fullJoin(pets, eq(users.id, pets.ownerId))

select ... from "users" full join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
    user: {
        id: number;
        name: string;
    } | null;
    pets: {
        id: number;
        name: string;
        ownerId: number;
    } | null;
}[];

交叉连接

const result = await db.select().from(users).crossJoin(pets)

select ... from "users" cross join "pets"

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    pets: {
        id: number;
        name: string;
        ownerId: number;
    };
}[];

横向交叉连接

const subquery = db.select().from(pets).where(gte(users.age, 16)).as('userPets')
const result = await db.select().from(users).crossJoinLateral(subquery)

select ... from "users" cross join lateral (select ... from "pets" where "users"."age" >= 16) "userPets"

// result type
const result: {
    user: {
        id: number;
        name: string;
    };
    userPets: {
        id: number;
        name: string;
        ownerId: number;
    };
}[];

部分选择

如果你需要选择特定的字段子集或使用扁平的响应类型，Drizzle ORM 支持使用部分查询的连接，并将根据 .select({ ... }) 结构自动推断返回类型。

await db.select({
  userId: users.id,
  petId: pets.id,
}).from(user).leftJoin(pets, eq(users.id, pets.ownerId))

select "users"."id", "pets"."id" from "users" left join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
  userId: number;
  petId: number | null;
}[];

你可能已经注意到 petId 现在可以为空，这是因为我们处于加入状态，并且可能存在没有宠物的用户。

请务必记住，在使用 sql 运算符进行部分选择字段和聚合操作时，你应该使用 sql<type | null> 进行正确的结果类型推断，这取决于你！

const result = await db.select({
  userId: users.id,
  petId: pets.id,
  petName1: sql`upper(${pets.name})`,
  petName2: sql<string | null>`upper(${pets.name})`,
  //˄we should explicitly tell 'string | null' in type, since we're left joining that field
}).from(user).leftJoin(pets, eq(users.id, pets.ownerId))

select "users"."id", "pets"."id", upper("pets"."name")... from "users" left join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
  userId: number;
  petId: number | null;
  petName1: unknown;
  petName2: string | null;
}[];

为了避免在连接具有大量列的表时出现过多的可空字段，我们可以利用嵌套的 select 对象语法，我们的智能类型推断将使整个对象可空，而不是使所有表字段可空！

await db.select({
  userId: users.id,
  userName: users.name,
  pet: {
    id: pets.id,
    name: pets.name,
    upperName: sql<string>`upper(${pets.name})`
  }
}).from(user).fullJoin(pets, eq(users.id, pets.ownerId))

select ... from "users" full join "pets" on "users"."id" = "pets"."owner_id"

// result type
const result: {
    userId: number | null;
    userName: string | null;
    pet: {
        id: number;
        name: string;
        upperName: string;
    } | null;
}[];

别名和自连接

Drizzle ORM 支持表别名，这在你需要进行自连接时非常方便。

假设你需要获取用户及其父级：

index.ts

schema.ts

import { user } from "./schema";

const parent = alias(user, "parent");
const result = db
  .select()
  .from(user)
  .leftJoin(parent, eq(parent.id, user.parentId));

select ... from "user" left join "user" "parent" on "parent"."id" = "user"."parent_id"

// result type
const result: {
    user: {
        id: number;
        name: string;
        parentId: number;
    };
    parent: {
        id: number;
        name: string;
        parentId: number;
    } | null;
}[];

export const user = pgTable("user", {
  id: integer("id").primaryKey({ autoIncrement: true }),
  name: text("name").notNull(),
  parentId: integer("parent_id").notNull().references((): AnyPgColumn => user.id)
});

聚合结果

Drizzle ORM 提供来自驱动程序的名称映射结果，而无需更改结构。

你可以自由地按照你想要的方式操作结果，以下是映射多对一关系数据的示例：

type User = typeof users.$inferSelect;
type Pet = typeof pets.$inferSelect;

const rows = db.select({
    user: users,
    pet: pets,
  }).from(users).leftJoin(pets, eq(users.id, pets.ownerId)).all();

const result = rows.reduce<Record<number, { user: User; pets: Pet[] }>>(
  (acc, row) => {
    const user = row.user;
    const pet = row.pet;

    if (!acc[user.id]) {
      acc[user.id] = { user, pets: [] };
    }

    if (pet) {
      acc[user.id].pets.push(pet);
    }

    return acc;
  },
  {}
);

// result type
const result: Record<number, {
    user: User;
    pets: Pet[];
}>;

多对一示例

import { sqliteTable, text, integer } from 'drizzle-orm/sqlite-core';
import { drizzle } from 'drizzle-orm/better-sqlite3';

const cities = sqliteTable('cities', {
  id: integer('id').primaryKey(),
  name: text('name'),
});

const users = sqliteTable('users', {
  id: integer('id').primaryKey(),
  name: text('name'),
  cityId: integer('city_id').references(() => cities.id)
});

const db = drizzle();

const result = db.select().from(cities).leftJoin(users, eq(cities.id, users.cityId)).all();

多对多示例

const users = sqliteTable('users', {
  id: integer('id').primaryKey(),
  name: text('name'),
});

const chatGroups = sqliteTable('chat_groups', {
  id: integer('id').primaryKey(),
  name: text('name'),
});

const usersToChatGroups = sqliteTable('usersToChatGroups', {
  userId: integer('user_id').notNull().references(() => users.id),
  groupId: integer('group_id').notNull().references(() => chatGroups.id),
});


// querying user group with id 1 and all the participants(users)
db.select()
  .from(usersToChatGroups)
  .leftJoin(users, eq(usersToChatGroups.userId, users.id))
  .leftJoin(chatGroups, eq(usersToChatGroups.groupId, chatGroups.id))
  .where(eq(chatGroups.id, 1))
  .all();