diff --git a/app/__test__/api/DataApi.spec.ts b/app/__test__/api/DataApi.spec.ts
index 2e4e4c5..c6bb3df 100644
--- a/app/__test__/api/DataApi.spec.ts
+++ b/app/__test__/api/DataApi.spec.ts
@@ -40,19 +40,17 @@ describe("DataApi", () => {
 
       {
          const res = (await app.request("/entity/posts")) as Response;
-         const { data } = await res.json();
+         const { data } = (await res.json()) as any;
          expect(data.length).toEqual(3);
       }
 
       // @ts-ignore tests
-      const api = new DataApi({ basepath: "/", queryLengthLimit: 50 });
-      // @ts-ignore protected
-      api.fetcher = app.request as typeof fetch;
+      const api = new DataApi({ basepath: "/", queryLengthLimit: 50 }, app.request as typeof fetch);
       {
          const req = api.readMany("posts", { select: ["title"] });
          expect(req.request.method).toBe("GET");
          const res = await req;
-         expect(res.data).toEqual(payload);
+         expect(res.data).toEqual(payload as any);
       }
 
       {
@@ -64,7 +62,151 @@ describe("DataApi", () => {
          });
          expect(req.request.method).toBe("POST");
          const res = await req;
-         expect(res.data).toEqual(payload);
+         expect(res.data).toEqual(payload as any);
+      }
+   });
+
+   it("updates many", async () => {
+      const schema = proto.em({
+         posts: proto.entity("posts", { title: proto.text(), count: proto.number() }),
+      });
+      const em = schemaToEm(schema);
+      await em.schema().sync({ force: true });
+
+      const payload = [
+         { title: "foo", count: 0 },
+         { title: "bar", count: 0 },
+         { title: "baz", count: 0 },
+         { title: "bla", count: 2 },
+      ];
+      await em.mutator("posts").insertMany(payload);
+
+      const ctx: any = { em, guard: new Guard() };
+      const controller = new DataController(ctx, dataConfig);
+      const app = controller.getController();
+
+      // @ts-ignore tests
+      const api = new DataApi({ basepath: "/" }, app.request as typeof fetch);
+      {
+         const req = api.readMany("posts", {
+            select: ["title", "count"],
+         });
+         const res = await req;
+         expect(res.data).toEqual(payload as any);
+      }
+
+      {
+         // update with empty where
+         expect(() => api.updateMany("posts", {}, { count: 1 })).toThrow();
+         expect(() => api.updateMany("posts", undefined, { count: 1 })).toThrow();
+      }
+
+      {
+         // update
+         const req = await api.updateMany("posts", { count: 0 }, { count: 1 });
+         expect(req.res.status).toBe(200);
+      }
+
+      {
+         // compare
+         const res = await api.readMany("posts", {
+            select: ["title", "count"],
+         });
+         expect(res.map((p) => p.count)).toEqual([1, 1, 1, 2]);
+      }
+   });
+
+   it("refines", async () => {
+      const schema = proto.em({
+         posts: proto.entity("posts", { title: proto.text() }),
+      });
+      const em = schemaToEm(schema);
+      await em.schema().sync({ force: true });
+
+      const payload = [{ title: "foo" }, { title: "bar" }, { title: "baz" }];
+      await em.mutator("posts").insertMany(payload);
+
+      const ctx: any = { em, guard: new Guard() };
+      const controller = new DataController(ctx, dataConfig);
+      const app = controller.getController();
+
+      const api = new DataApi({ basepath: "/" }, app.request as typeof fetch);
+      const normalOne = api.readOne("posts", 1);
+      const normal = api.readMany("posts", { select: ["title"], where: { title: "baz" } });
+      expect((await normal).data).toEqual([{ title: "baz" }] as any);
+
+      // refine
+      const refined = normal.refine((data) => data[0]);
+      expect((await refined).data).toEqual({ title: "baz" } as any);
+
+      // one
+      const oneBy = api.readOneBy("posts", { where: { title: "baz" }, select: ["title"] });
+      const oneByRes = await oneBy;
+      expect(oneByRes.data).toEqual({ title: "baz" } as any);
+      expect(oneByRes.body.meta.count).toEqual(1);
+   });
+
+   it("exists/count", async () => {
+      const schema = proto.em({
+         posts: proto.entity("posts", { title: proto.text() }),
+      });
+      const em = schemaToEm(schema);
+      await em.schema().sync({ force: true });
+
+      const payload = [{ title: "foo" }, { title: "bar" }, { title: "baz" }];
+      await em.mutator("posts").insertMany(payload);
+
+      const ctx: any = { em, guard: new Guard() };
+      const controller = new DataController(ctx, dataConfig);
+      const app = controller.getController();
+
+      const api = new DataApi({ basepath: "/" }, app.request as typeof fetch);
+
+      const exists = api.exists("posts", { id: 1 });
+      expect((await exists).exists).toBeTrue();
+
+      expect((await api.count("posts")).count).toEqual(3);
+   });
+
+   it("creates many", async () => {
+      const schema = proto.em({
+         posts: proto.entity("posts", { title: proto.text(), count: proto.number() }),
+      });
+      const em = schemaToEm(schema);
+      await em.schema().sync({ force: true });
+
+      const payload = [
+         { title: "foo", count: 0 },
+         { title: "bar", count: 0 },
+         { title: "baz", count: 0 },
+         { title: "bla", count: 2 },
+      ];
+
+      const ctx: any = { em, guard: new Guard() };
+      const controller = new DataController(ctx, dataConfig);
+      const app = controller.getController();
+
+      // @ts-ignore tests
+      const api = new DataApi({ basepath: "/" }, app.request as typeof fetch);
+
+      {
+         // create many
+         const res = await api.createMany("posts", payload);
+         expect(res.data.length).toEqual(4);
+         expect(res.ok).toBeTrue();
+      }
+
+      {
+         const req = api.readMany("posts", {
+            select: ["title", "count"],
+         });
+         const res = await req;
+         expect(res.data).toEqual(payload as any);
+      }
+
+      {
+         // create with empty
+         expect(() => api.createMany("posts", [])).toThrow();
       }
    });
 });
diff --git a/app/__test__/api/ModuleApi.spec.ts b/app/__test__/api/ModuleApi.spec.ts
index 59c8816..6f65567 100644
--- a/app/__test__/api/ModuleApi.spec.ts
+++ b/app/__test__/api/ModuleApi.spec.ts
@@ -89,6 +89,14 @@ describe("ModuleApi", () => {
       expect(api.delete("/").request.method).toEqual("DELETE");
    });
 
+   it("refines", async () => {
+      const app = new Hono().get("/endpoint", (c) => c.json({ foo: ["bar"] }));
+      const api = new Api({ host }, app.request as typeof fetch);
+
+      expect((await api.get("/endpoint")).data).toEqual({ foo: ["bar"] });
+      expect((await api.get("/endpoint").refine((data) => data.foo)).data).toEqual(["bar"]);
+   });
+
    // @todo: test error response
    // @todo: test method shortcut functions
 });
diff --git a/app/__test__/data/mutation.simple.test.ts b/app/__test__/data/mutation.simple.test.ts
index 8fb0a33..f425733 100644
--- a/app/__test__/data/mutation.simple.test.ts
+++ b/app/__test__/data/mutation.simple.test.ts
@@ -137,7 +137,7 @@ describe("Mutator simple", async () => {
       expect((await em.repository(items).findMany()).data.length).toBe(data.length - 2);
       //console.log((await em.repository(items).findMany()).data);
 
-      await em.mutator(items).deleteWhere();
+      await em.mutator(items).deleteWhere({ id: { $isnull: 0 } });
       expect((await em.repository(items).findMany()).data.length).toBe(0);
 
       //expect(res.data.count).toBe(0);
diff --git a/app/package.json b/app/package.json
index 074b291..7b4d8c0 100644
--- a/app/package.json
+++ b/app/package.json
@@ -3,7 +3,7 @@
   "type": "module",
   "sideEffects": false,
   "bin": "./dist/cli/index.js",
-  "version": "0.9.0-rc.2",
+  "version": "0.9.0-rc.3",
   "description": "Lightweight Firebase/Supabase alternative built to run anywhere — incl. Next.js, Remix, Astro, Cloudflare, Bun, Node, AWS Lambda & more.",
   "homepage": "https://bknd.io",
   "repository": {
diff --git a/app/src/data/api/DataApi.ts b/app/src/data/api/DataApi.ts
index bff63e7..0819b08 100644
--- a/app/src/data/api/DataApi.ts
+++ b/app/src/data/api/DataApi.ts
@@ -1,6 +1,7 @@
 import type { DB } from "core";
 import type { EntityData, RepoQueryIn, RepositoryResponse } from "data";
 import { type BaseModuleApiOptions, ModuleApi, type PrimaryFieldType } from "modules";
+import type { FetchPromise, ResponseObject } from "modules/ModuleApi";
 
 export type DataApiOptions = BaseModuleApiOptions & {
    queryLengthLimit: number;
@@ -18,6 +19,12 @@ export class DataApi extends ModuleApi<DataApiOptions> {
       };
    }
 
+   private requireObjectSet(obj: any, message?: string) {
+      if (!obj || typeof obj !== "object" || Object.keys(obj).length === 0) {
+         throw new Error(message ?? "object is required");
+      }
+   }
+
    readOne<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
       entity: E,
       id: PrimaryFieldType,
@@ -29,6 +36,18 @@ export class DataApi extends ModuleApi<DataApiOptions> {
       );
    }
 
+   readOneBy<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
+      entity: E,
+      query: Omit<RepoQueryIn, "limit" | "offset" | "sort"> = {},
+   ) {
+      type T = Pick<RepositoryResponse<Data>, "meta" | "data">;
+      return this.readMany(entity, {
+         ...query,
+         limit: 1,
+         offset: 0,
+      }).refine((data) => data[0]) as unknown as FetchPromise<ResponseObject<T>>;
+   }
+
    readMany<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
       entity: E,
       query: RepoQueryIn = {},
@@ -63,25 +82,64 @@ export class DataApi extends ModuleApi<DataApiOptions> {
       return this.post<RepositoryResponse<Data>>(["entity", entity as any], input);
    }
 
+   createMany<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
+      entity: E,
+      input: Omit<Data, "id">[],
+   ) {
+      if (!input || !Array.isArray(input) || input.length === 0) {
+         throw new Error("input is required");
+      }
+      return this.post<RepositoryResponse<Data[]>>(["entity", entity as any], input);
+   }
+
    updateOne<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
       entity: E,
       id: PrimaryFieldType,
       input: Partial<Omit<Data, "id">>,
    ) {
+      if (!id) throw new Error("ID is required");
       return this.patch<RepositoryResponse<Data>>(["entity", entity as any, id], input);
    }
 
+   updateMany<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
+      entity: E,
+      where: RepoQueryIn["where"],
+      update: Partial<Omit<Data, "id">>,
+   ) {
+      this.requireObjectSet(where);
+      return this.patch<RepositoryResponse<Data[]>>(["entity", entity as any], {
+         update,
+         where,
+      });
+   }
+
    deleteOne<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
       entity: E,
       id: PrimaryFieldType,
    ) {
+      if (!id) throw new Error("ID is required");
       return this.delete<RepositoryResponse<Data>>(["entity", entity as any, id]);
    }
 
+   deleteMany<E extends keyof DB | string, Data = E extends keyof DB ? DB[E] : EntityData>(
+      entity: E,
+      where: RepoQueryIn["where"],
+   ) {
+      this.requireObjectSet(where);
+      return this.delete<RepositoryResponse<Data>>(["entity", entity as any], where);
+   }
+
    count<E extends keyof DB | string>(entity: E, where: RepoQueryIn["where"] = {}) {
       return this.post<RepositoryResponse<{ entity: E; count: number }>>(
          ["entity", entity as any, "fn", "count"],
          where,
       );
    }
+
+   exists<E extends keyof DB | string>(entity: E, where: RepoQueryIn["where"] = {}) {
+      return this.post<RepositoryResponse<{ entity: E; exists: boolean }>>(
+         ["entity", entity as any, "fn", "exists"],
+         where,
+      );
+   }
 }
diff --git a/app/src/data/api/DataController.ts b/app/src/data/api/DataController.ts
index 232d463..5aae943 100644
--- a/app/src/data/api/DataController.ts
+++ b/app/src/data/api/DataController.ts
@@ -343,14 +343,20 @@ export class DataController extends Controller {
          "/:entity",
          permission(DataPermissions.entityCreate),
          tb("param", Type.Object({ entity: Type.String() })),
+         tb("json", Type.Union([Type.Object({}), Type.Array(Type.Object({}))])),
          async (c) => {
             const { entity } = c.req.param();
             if (!this.entityExists(entity)) {
                return this.notFound(c);
             }
-            const body = (await c.req.json()) as EntityData;
-            const result = await this.em.mutator(entity).insertOne(body);
+            const body = (await c.req.json()) as EntityData | EntityData[];
 
+            if (Array.isArray(body)) {
+               const result = await this.em.mutator(entity).insertMany(body);
+               return c.json(this.mutatorResult(result), 201);
+            }
+
+            const result = await this.em.mutator(entity).insertOne(body);
             return c.json(this.mutatorResult(result), 201);
          },
       );
diff --git a/app/src/data/entities/Mutator.ts b/app/src/data/entities/Mutator.ts
index d6f49db..fcac3ef 100644
--- a/app/src/data/entities/Mutator.ts
+++ b/app/src/data/entities/Mutator.ts
@@ -270,9 +270,14 @@ export class Mutator<
    }
 
    // @todo: decide whether entries should be deleted all at once or one by one (for events)
-   async deleteWhere(where?: RepoQuery["where"]): Promise<MutatorResponse<Output[]>> {
+   async deleteWhere(where: RepoQuery["where"]): Promise<MutatorResponse<Output[]>> {
       const entity = this.entity;
 
+      // @todo: add a way to delete all by adding force?
+      if (!where || typeof where !== "object" || Object.keys(where).length === 0) {
+         throw new Error("Where clause must be provided for mass deletion");
+      }
+
       const qb = this.appendWhere(this.conn.deleteFrom(entity.name), where).returning(
          entity.getSelect(),
       );
@@ -282,11 +287,16 @@ export class Mutator<
 
    async updateWhere(
       data: Partial<Input>,
-      where?: RepoQuery["where"],
+      where: RepoQuery["where"],
    ): Promise<MutatorResponse<Output[]>> {
       const entity = this.entity;
       const validatedData = await this.getValidatedData(data, "update");
 
+      // @todo: add a way to delete all by adding force?
+      if (!where || typeof where !== "object" || Object.keys(where).length === 0) {
+         throw new Error("Where clause must be provided for mass update");
+      }
+
       const query = this.appendWhere(this.conn.updateTable(entity.name), where)
          .set(validatedData as any)
          .returning(entity.getSelect());
diff --git a/app/src/modules/ModuleApi.ts b/app/src/modules/ModuleApi.ts
index a5b4a69..d5f8ed5 100644
--- a/app/src/modules/ModuleApi.ts
+++ b/app/src/modules/ModuleApi.ts
@@ -148,9 +148,10 @@ export abstract class ModuleApi<Options extends BaseModuleApiOptions = BaseModul
       });
    }
 
-   delete<Data = any>(_input: TInput, _init?: RequestInit) {
+   delete<Data = any>(_input: TInput, body?: any, _init?: RequestInit) {
       return this.request<Data>(_input, undefined, {
          ..._init,
+         body,
          method: "DELETE",
       });
    }
@@ -171,7 +172,7 @@ export function createResponseProxy<Body = any, Data = any>(
    body: Body,
    data?: Data,
 ): ResponseObject<Body, Data> {
-   let actualData: any = data ?? body;
+   let actualData: any = typeof data !== "undefined" ? data : body;
    const _props = ["raw", "body", "ok", "status", "res", "data", "toJSON"];
 
    // that's okay, since you have to check res.ok anyway
@@ -189,6 +190,7 @@ export function createResponseProxy<Body = any, Data = any>(
          if (prop === "toJSON") {
             return () => target;
          }
+
          return Reflect.get(target, prop, receiver);
       },
       has(target, prop) {
@@ -223,12 +225,19 @@ export class FetchPromise<T = ApiResponse<any>> implements Promise<T> {
          fetcher?: typeof fetch;
          verbose?: boolean;
       },
+      protected refineData?: (data: T) => any,
    ) {}
 
    get verbose() {
       return this.options?.verbose ?? false;
    }
 
+   refine<N>(fn: (data: T) => N) {
+      return new FetchPromise(this.request, this.options, fn) as unknown as FetchPromise<
+         ApiResponse<N>
+      >;
+   }
+
    async execute(): Promise<ResponseObject<T>> {
       // delay in dev environment
       isDebug() && (await new Promise((resolve) => setTimeout(resolve, 200)));
@@ -265,6 +274,15 @@ export class FetchPromise<T = ApiResponse<any>> implements Promise<T> {
          resBody = res.body;
       }
 
+      if (this.refineData) {
+         try {
+            resData = this.refineData(resData);
+         } catch (e) {
+            console.warn("[FetchPromise] Error in refineData", e);
+            resData = undefined;
+         }
+      }
+
       return createResponseProxy<T>(res, resBody, resData);
    }
 
diff --git a/docs/usage/sdk.mdx b/docs/usage/sdk.mdx
index 919a8ee..e5b5825 100644
--- a/docs/usage/sdk.mdx
+++ b/docs/usage/sdk.mdx
@@ -88,14 +88,32 @@ const { data } = await api.data.readMany("posts", {
    limit: 10,
    offset: 0,
    select: ["id", "title", "views"],
-   with: ["comments"],
+   with: {
+      // join last 2 comments
+      comments: {
+         with: {
+            // along with the comments' user
+            users: {}
+         },
+         limit: 2,
+         sort: "-id"
+      },
+      // also get the first 2 images, but only the path
+      images: {
+         select: ["path"],
+         limit: 2
+      }
+   },
    where: {
+      // same as '{ title: { $eg: "Hello, World!" } }'
       title: "Hello, World!",
+      // only with views greater than 100
       views: {
          $gt: 100
       }
    },
-   sort: { by: "views", order: "desc" }
+   // sort by views descending (without "-" would be ascending)
+   sort: "-views"
 });
 ```
 The `with` property automatically adds the related entries to the response.
@@ -116,6 +134,15 @@ const { data } = await api.data.createOne("posts", {
 });
 ```
 
+### `data.createMany([entity], [data])`
+To create many records of an entity, use the `createMany` method:
+```ts
+const { data } = await api.data.createMany("posts", [
+   { title: "Hello, World!" },
+   { title: "Again, Hello." },
+]);
+```
+
 ### `data.updateOne([entity], [id], [data])`
 To update a single record of an entity, use the `updateOne` method:
 ```ts
@@ -124,12 +151,26 @@ const { data } = await api.data.updateOne("posts", 1, {
 });
 ```
 
+### `data.updateMany([entity], [where], [update])`
+To update many records of an entity, use the `updateMany` method:
+```ts
+const { data } = await api.data.updateMany("posts", { views: { $gt: 1 } }, {
+   title: "viewed more than once"
+});
+```
+
 ### `data.deleteOne([entity], [id])`
 To delete a single record of an entity, use the `deleteOne` method:
 ```ts
 const { data } = await api.data.deleteOne("posts", 1);
 ```
 
+### `data.deleteMany([entity], [where])`
+To delete many records of an entity, use the `deleteMany` method:
+```ts
+const { data } = await api.data.deleteMany("posts", { views: { $lte: 1 } });
+```
+
 ## Auth (`api.auth`)
 Access the `Auth` specific API methods at `api.auth`. If there is successful authentication, the
 API will automatically save the token and use it for subsequent requests.