add note about env vars when using driver adapters

content/200-orm/050-overview/500-databases/200-database-drivers.mdx

@@ -7,7 +7,7 @@ tocDepth: 4
 
 ## Default built-in drivers
 
-One of Prisma Client's components is the [Query Engine](/orm/more/under-the-hood/engines) . The Query Engine is responsible for transforming Prisma Client queries to SQL statements. The Query Engine connects to your database using the included drivers that don't require additional setup. The built-in drivers use TCP connections to connect to the database.
+One of Prisma Client's components is the [Query Engine](/orm/more/under-the-hood/engines). The Query Engine is responsible for transforming Prisma Client queries to SQL statements. The Query Engine connects to your database via TCP using built-in drivers that don't require additional setup.
 
 ![Query flow from the user application to the database with Prisma Client](./images/drivers/qe-query-execution-flow.png)
 
@@ -19,7 +19,7 @@ Prisma Client will use the Query Engine to transform the Prisma Client query to
 
 ![Query flow from the user application to the database using Prisma Client and driver adapters](./images/drivers/qe-query-engine-adapter.png)
 
-There are 2 different types of driver adapters:
+There are two different types of driver adapters:
 
 - [Database driver adapters](#database-driver-adapters)
 - [Serverless driver adapters](#serverless-driver-adapters)
@@ -40,13 +40,13 @@ Prisma ORM maintains the following serverless driver adapters:
 - [Neon](/orm/overview/databases/neon#how-to-use-neons-serverless-driver-with-prisma-orm-preview)
 - [PlanetScale](/orm/overview/databases/planetscale#how-to-use-the-planetscale-serverless-driver-with-prisma-orm-preview)
 
-## Community maintained database driver adapters
+### Community-maintained database driver adapters
 
 You can also build your own driver adapter for the database you're using. The following is a list of community maintained driver adapters:
 
 - [TiDB](https://github.com/tidbcloud/prisma-adapter)
 
-### How to use driver adapters
+## How to use driver adapters
 
 To use this feature:
 
@@ -71,6 +71,26 @@ To use this feature:
    - [PlanetScale](/orm/overview/databases/planetscale#how-to-use-the-planetscale-serverless-driver-with-prisma-orm-preview)
    - [Turso](/orm/overview/databases/turso#how-to-connect-and-query-a-turso-database)
 
+## Notes about using driver adapters
+
+### Driver adapters don't read the connection string from the Prisma schema
+
+When using Prisma ORM's built-in drivers, the connection string is read from the `url` field of the `datasource` block in your Prisma schema.
+
+On the other hand, when using a driver adapter, the connection string needs to be provided in your _application code_ when the driver adapter is set up initially. Here is how this is done for the `pg` driver and the `@prisma/adapter-pg` adapter:
+
+```ts highlight=5,normal
+import { PrismaClient } from '@prisma/client'
+import { PrismaPg } from '@prisma/adapter-pg'
+import { Pool } from 'pg'
+
+const pool = new Pool({ connectionString: env.DATABASE_URL })
+const adapter = new PrismaPg(pool)
+const prisma = new PrismaClient({ adapter })
+```
+
+See the docs for the driver adapter you're using for concrete setup instructions.
+
 ### Driver adapters and custom output paths
 
 Since Prisma 5.9.0, when using the driver adapters Preview feature along with a [custom output path for Prisma Client](/orm/prisma-client/setup-and-configuration/generating-prisma-client#using-a-custom-output-path), you cannot reference Prisma Client using a relative path.