Merge branch 'docs/typeorm' of https://github.com/Sikora00/docs.nestjs.com into Sikora00-docs/typeorm

Author: kamilmysliwiec

content/techniques/sql.md

@@ -358,6 +358,64 @@ With that option specified, every entity registered through the `forFeature()` m
 
 > warning **Warning** Note that entities that aren't registered through the `forFeature()` method, but are only referenced from the entity (via a relationship), won't be included by way of the `autoLoadEntities` setting.
 
+#### Separating Entity Definition
+
+You can define an entity and its columns right in the model, using decorators. But some people prefer to define an entity and its columns inside separate files which are called ["entity schemas"](https://typeorm.io/#/separating-entity-definition).
+
+
+```typescript
+import { EntitySchema } from 'typeorm';
+import { User } from './user.entity';
+
+export const UserSchema = new EntitySchema<User>({
+    name: 'User',
+    target: User,
+    columns: {
+        id: {
+            type: Number,
+            primary: true,
+            generated: true
+        },
+        firstName: {
+            type: String
+        },
+        lastName: {
+            type: String
+        },
+        isActive: {
+            type: Boolean,
+            default: true
+        }
+    },
+    relations: {
+        photos: {
+            type: 'one-to-many',
+            target: 'Photo' // The name of the PhotoSchema
+        }
+    }
+});
+```
+> error **Warning** If you provide the `target` option, the `name` option value has to be the same as the name of the target class.
+> If you do not provide the `target` you can use any name.
+
+
+Nest allows you to use an `EntitySchema` instance wherever an `Entity` is expected, for example:
+
+```typescript
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { UserSchema } from './user.schema';
+import { UsersController } from './users.controller';
+import { UsersService } from './users.service';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([UserSchema])],
+  providers: [UsersService],
+  controllers: [UsersController],
+})
+export class UsersModule {}
+```
+
 #### Transactions
 
 A database transaction symbolizes a unit of work performed within a database management system against a database, and treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database ([learn more](https://en.wikipedia.org/wiki/Database_transaction)).