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