Add Open Connections To Multiple Databases as a Prisma TIL

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1306 TILs and counting..._
+_1307 TILs and counting..._
 
 ---
 
@@ -745,6 +745,7 @@ _1306 TILs and counting..._
 - [Batch Insert Records With createMany](prisma/batch-insert-records-with-create-many.md)
 - [Execute A Raw SQL Query](prisma/execute-a-raw-sql-query.md)
 - [Grab A Limited Set Of Records](prisma/grab-a-limited-set-of-records.md)
+- [Open Connections To Multiple Databases](prisma/open-connections-to-multiple-databases.md)
 - [Specify Alternate Location For Prisma Schema](prisma/specify-alternate-location-for-prisma-schema.md)
 
 ### Python

prisma/open-connections-to-multiple-databases.md

@@ -0,0 +1,39 @@
+# Open Connections To Multiple Databases
+
+A standard database connection with Prisma is determined by a `DATABASE_URL`
+env var set in the `.env` file of your project. Typically, the Prisma client
+connecting to that URL will be configured in a separate file and imported
+wherever it is used.
+
+```javascript
+import {prisma} from './utils/prisma'
+```
+
+What if you want to connect to a second, alternate database?
+
+You can create a new Prisma client with the data source configured to be a
+different connection URL.
+
+```javascript
+import {prisma as primaryPrismaClient} from '@skillrecordings/database'
+import {PrismaClient} from '@prisma/client'
+
+const secondaryDatabaseUrl = 'mysql://root@localhost:3399/my-database'
+
+const secondaryPrismaClient = new PrismaClient({
+  datasources: {
+    db: {
+      url: secondaryDatabaseUrl
+    }
+  },
+})
+```
+
+And with that, you can execute queries against both databases.
+
+```javascript
+const primaryUserCount = await primaryPrismaClient.user.count()
+const secondaryUserCount = await secondaryPrismaClient.user.count()
+```
+
+[source](https://www.prisma.io/docs/reference/api-reference/prisma-client-reference#programmatically-override-a-datasource-url)