new: PostgreSQL WITH and INSERT ... RETURNING statements

INSERT ... RETURNING.md

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+---
+tags: database, potsgresql, sql
+---
+
+# INSERT ... RETURNING
+
+You can return any information about any inserted element in the `INSERT` statement by using the `RETURNING ...` clause
+
+## Example
+
+```sql
+INSERT INTO roles (name)
+VALUES ('master')
+RETURNING role_id
+```
+
+So after `RETURNING` you choose all the columns you want to get
+
+Very useful along [[The WITH statement]] to chain a bunch of insertions atomically without using transactions
+
+---
+
+## What led to learning this
+
+- Started using the SQL language in PostgreSQL. Working on a [tiny family project](https://github.com/taionca/taionca/)

The WITH statement.md

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+---
+tags: database, potsgresql, transaction, sql
+---
+
+# The WITH statement
+
+Allows to save into variables tables results returned from a `SELECT` or [[INSERT ... RETURNING]] statement, and use them in following querys.
+
+Also allows to chain multiple `INSERTS`, and if any of them fails, all previous `INSERTS` are rolledback.\
+*Note: autoincrements still increase on failures, hence skipped.*
+
+So It's excellent to avoid explicitly using transactions
+
+## Example
+
+```sql
+WITH inserted_user as (
+    INSERT INTO users (username, name, password_hash)
+    VALUES ('master', 'master', '$argon2i$v=19$m=4096,t=10,p=1$l9mKHF/++OJO4Fzj5VvOxw$smezKrrynx74W2+7L4zyiKUXWFdQDqdKf2RBMU4p0JI')
+    RETURNING user_id
+), inserted_role as (
+    INSERT INTO roles (name)
+    VALUES ('master')
+    RETURNING role_id
+), t as (
+    INSERT INTO join_users_roles (user_id, role_id)
+    SELECT user_id, role_id
+    FROM inserted_user, inserted_role
+)
+INSERT INTO join_roles_permissions (role_id, permission_id)
+SELECT role_id, permission_id FROM inserted_role, permissions;
+```
+
+## What led to learning this
+
+- Needed to insert a bunch of data atomically accross many tables, see the [example](#example) above. Working on a [tiny family project](https://github.com/taionca/taionca/)