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Yii v2 snippet guide II

Revision #40 has been created by rackycz on Oct 5, 2020, 6:31:14 PM with the memo:

Child aggregation in Parent GridView
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Yii v2 snippet guide II

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Tutorials

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2.0

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tutorial,beginner,yii2,snippets

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[...]
```sql
CREATE VIEW v_invoice AS
SELECT invoice.*,
SUM(invoice_item.units * invoice_item.price_per_unit) as amount,
COUNT(*count(invoice_item.id) as items
FROM invoice
LEFT JOIN invoice_item
[...]
```

**Note:** Here you can read why it is better not to use COUNT(*):
 
- [https://learnsql.com/blog/introduction-using-aggregate-functions-joins/](https://learnsql.com/blog/introduction-using-aggregate-functions-joins/)
 
- Chapter: Dealing with NULLs
 
 
This will technically clone the original table "invoice" into "v_invoice" and will append 2 calculated columns: "amount" + "items". Now you can easily use this VIEW as a TABLE (for reading only) and display it in a GridView. If you already have a GridView for table "invoice" the change is just tiny. Create this model:

```php
<?php
namespace app\models;
class v_Invoice extends Invoice
[...]
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Viewed: 75 361 times
Version: 2.0
Category: Tutorials
Tags: beginner, snippets, tutorial, yii2
Written by: rackycz
Last updated by: rackycz
Created on: Aug 26, 2020
Last updated: 3 years ago
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