diff --git a/TODO.md b/TODO.md
index c1c4e50..13a05d6 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,12 +1,16 @@
 - [ ] Integrate with other data stores
   - [ ] SQLite
   - [ ] PostgreSQL
+  - [ ] DuckDB
 - [X] Access control with resources
 - [ ] Custom definitions
   - [ ] Middlewares
   - [ ] Request decorators
   - [ ] Status messages
   - [ ] Response bodies (in case of error messages)
+  - [ ] Resource operations
+    - [ ] Single item
+    - [ ] Collection
 - [ ] Content negotiation
   - [X] Language
   - [X] Charset
@@ -32,3 +36,4 @@
   - [ ] Swagger docs plugin
     - [ ] Plugin support
 - [ ] Add option to reject content negotiation params with `406 Not Acceptable`
+- [ ] Add `fast-check` for property-based checking
diff --git a/packages/core/test/features/decorators.test.ts b/packages/core/test/features/decorators.test.ts
index 09d8b2e..f1824ec 100644
--- a/packages/core/test/features/decorators.test.ts
+++ b/packages/core/test/features/decorators.test.ts
@@ -71,6 +71,7 @@ describe('decorators', () => {
 				resolve();
 			});
 
+			// TODO add .inject() method
 			server.listen({
 				port: PORT
 			});
diff --git a/packages/data-sources/duckdb/src/index.ts b/packages/data-sources/duckdb/src/index.ts
index 37a3f65..a25fba7 100644
--- a/packages/data-sources/duckdb/src/index.ts
+++ b/packages/data-sources/duckdb/src/index.ts
@@ -5,9 +5,38 @@ import assert from 'assert';
 
 type ID = number;
 
+interface DuckDbDataSourceBase<
+  ID,
+  Schema extends v.BaseSchema = v.BaseSchema,
+  CurrentName extends string = string,
+  CurrentRouteName extends string = string,
+  Data extends object = v.Output<Schema>,
+> extends DataSource<Data, ID> {
+  resource?: Resource<BaseResourceType & {
+    schema: Schema,
+    name: CurrentName,
+    routeName: CurrentRouteName,
+  }>;
+
+  db?: Database;
+}
+
 export const AutoincrementIdConfig = {
-  // TODO
-  generationStrategy: async () => {},
+  // TODO add options: https://duckdb.org/docs/sql/statements/create_sequence
+  generationStrategy: async (dataSourceRaw: DataSource) => {
+    const dataSource = dataSourceRaw as DuckDbDataSourceBase<ID>;
+    assert(typeof dataSource.db !== 'undefined');
+    assert(typeof dataSource.resource !== 'undefined');
+    const idAttr = dataSource.resource.state.shared.get('idAttr');
+    assert(typeof idAttr === 'string');
+
+    const con = await dataSource.db.connect();
+    const stmt = await con.prepare(`
+      SELECT nextval('${dataSource.resource.state.routeName}_sequence') as ${idAttr}; 
+    `);
+    const [v] = await stmt.all();
+    return v[idAttr];
+  },
   schema: v.number(),
   serialize: (v: unknown) => v?.toString() ?? '',
   deserialize: (v: string) => Number(v),
@@ -18,8 +47,8 @@ export class DuckDbDataSource<
   CurrentName extends string = string,
   CurrentRouteName extends string = string,
   Data extends object = v.Output<Schema>,
-> implements DataSource<Data, ID> {
-  private resource?: Resource<BaseResourceType & {
+> implements DuckDbDataSourceBase<ID, Schema, CurrentName, CurrentRouteName, Data> {
+  resource?: Resource<BaseResourceType & {
     schema: Schema,
     name: CurrentName,
     routeName: CurrentRouteName,
@@ -27,11 +56,12 @@ export class DuckDbDataSource<
 
   db?: Database;
 
-  constructor() {
+  constructor(private readonly path: string) {
     // noop
   }
 
   async initialize() {
+    assert(typeof this.path !== 'undefined');
     assert(typeof this.resource !== 'undefined');
 
     const idConfig = this.resource.state.shared.get('idConfig') as ResourceIdConfig<any> | undefined;
@@ -42,7 +72,7 @@ export class DuckDbDataSource<
 
     const idSchema = idConfig.schema as v.BaseSchema;
 
-    this.db = await Database.create('test.db');
+    this.db = await Database.create(this.path);
     const clause = `CREATE TABLE IF NOT EXISTS ${this.resource.state.routeName}`;
     const resourceSchema = this.resource.schema as unknown as v.ObjectSchema<any>;
     const tableSchema = Object.entries(resourceSchema.entries)
@@ -51,7 +81,16 @@ export class DuckDbDataSource<
         return [columnName, columnDef.type].join(' ');
       })
       .join(',');
-    const sql = `${clause} (${idAttr} ${idSchema.type},${tableSchema});`;
+    let sequenceSql = '';
+    let defaultValue = '';
+    let idType = 'STRING';
+    if (idSchema.type === 'number') {
+      // TODO support more sequence statements: https://duckdb.org/docs/sql/statements/create_sequence
+      sequenceSql = `CREATE SEQUENCE IF NOT EXISTS ${this.resource.state.routeName}_sequence START 1;`;
+      defaultValue = `DEFAULT nextval('${this.resource.state.routeName}_sequence')`;
+      idType = 'INTEGER';
+    }
+    const sql = `${sequenceSql}${clause} (${idAttr} ${idType} ${defaultValue},${tableSchema});`;
     const con = await this.db.connect();
     const stmt = await con.prepare(sql);
     await stmt.run();
@@ -77,7 +116,8 @@ export class DuckDbDataSource<
     this.resource = resource as any;
   }
 
-  async getMultiple() {
+  async getMultiple(query) {
+    // TODO translate query to SQL statements
     assert(typeof this.db !== 'undefined');
     assert(typeof this.resource !== 'undefined');
 
@@ -90,7 +130,8 @@ export class DuckDbDataSource<
   }
 
   async newId() {
-    const idConfig = this.resource?.state.shared.get('idConfig') as ResourceIdConfig<any>;
+    assert(typeof this.resource !== 'undefined');
+    const idConfig = this.resource.state.shared.get('idConfig') as ResourceIdConfig<any>;
     assert(typeof idConfig !== 'undefined');
 
     const theNewId = await idConfig.generationStrategy(this);
@@ -107,7 +148,18 @@ export class DuckDbDataSource<
     const idAttr = this.resource.state.shared.get('idAttr');
     assert(typeof idAttr === 'string');
 
-    const { [idAttr]: _, ...effectiveData } = data as Record<string, unknown>;
+    let theId: any;
+    const { [idAttr]: dataId } = data as Record<string, unknown>;
+    if (typeof dataId !== 'undefined') {
+      theId = idConfig.deserialize((data as Record<string, string>)[idAttr]);
+    } else {
+      const newId = await this.newId();
+      theId = idConfig.deserialize(newId.toString());
+    }
+    const effectiveData = {
+      ...data,
+    } as Record<string, unknown>;
+    effectiveData[idAttr] = theId;
 
     const clause = `INSERT INTO ${this.resource.state.routeName}`;
     const keys = Object.keys(effectiveData).join(',');
@@ -115,14 +167,14 @@ export class DuckDbDataSource<
     const sql = `${clause} (${keys}) VALUES (${values});`;
     const con = await this.db.connect();
     const stmt = await con.prepare(sql);
-    await stmt.all();
+    await stmt.run();
     const newData = {
       ...effectiveData
     };
     return newData as Data;
   }
 
-  async getTotalCount() {
+  async getTotalCount(query) {
     assert(typeof this.db !== 'undefined');
     assert(typeof this.resource !== 'undefined');
 
@@ -131,10 +183,10 @@ export class DuckDbDataSource<
 
     const con = await this.db.connect();
     const stmt = await con.prepare(`
-      SELECT COUNT(*) FROM ?;
-    `, this.resource.state.routeName);
+      SELECT COUNT(*) as c FROM ${this.resource.state.routeName};
+    `);
     const [data] = await stmt.all();
-    return data as unknown as number;
+    return data['c'] as unknown as number;
   }
 
   async getById(id: ID) {
@@ -148,11 +200,11 @@ export class DuckDbDataSource<
     const stmt = await con.prepare(`
       SELECT * FROM ${this.resource.state.routeName} WHERE ${idAttr} = ${JSON.stringify(id).replace(/"/g, "'")};
     `);
-    const data = await stmt.all();
-    return data as Data;
+    const [data = null] = await stmt.all();
+    return data as Data | null;
   }
 
-  async getSingle() {
+  async getSingle(query) {
     assert(typeof this.db !== 'undefined');
     assert(typeof this.resource !== 'undefined');
 
@@ -160,8 +212,8 @@ export class DuckDbDataSource<
     const stmt = await con.prepare(`
       SELECT * FROM ${this.resource.state.routeName} LIMIT 1;
     `);
-    const [data] = await stmt.all();
-    return data as Data;
+    const [data = null] = await stmt.all();
+    return data as Data | null;
   }
 
   async delete(id: ID) {
diff --git a/packages/examples/duckdb/.gitignore b/packages/examples/duckdb/.gitignore
index 53992de..b9f3b75 100644
--- a/packages/examples/duckdb/.gitignore
+++ b/packages/examples/duckdb/.gitignore
@@ -105,3 +105,5 @@ dist
 .tern-port
 
 .npmrc
+*.db
+*.db.wal
diff --git a/packages/examples/duckdb/src/index.ts b/packages/examples/duckdb/src/index.ts
index 228446a..9d76edf 100644
--- a/packages/examples/duckdb/src/index.ts
+++ b/packages/examples/duckdb/src/index.ts
@@ -27,8 +27,9 @@ const app = application({
   .resource(Post);
 
 const backend = app.createBackend({
-    dataSource: new DuckDbDataSource(),
+    dataSource: new DuckDbDataSource('test.db'),
   })
+  .showTotalItemCountOnGetCollection()
   .throwsErrorOnDeletingNotFound();
 
 const server = backend.createHttpServer({
diff --git a/packages/examples/duckdb/test.db b/packages/examples/duckdb/test.db
deleted file mode 100644
index 72cf332..0000000
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diff --git a/packages/examples/duckdb/test.db.wal b/packages/examples/duckdb/test.db.wal
deleted file mode 100644
index becce1b..0000000
Binary files a/packages/examples/duckdb/test.db.wal and /dev/null differ