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08855064
编写于
6月 01, 2014
作者:
M
Mauro George
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电子邮件补丁
差异文件
Add Total of grouped items to AR query interface on guides
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guides/source/active_record_querying.md
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guides/source/active_record_querying.md
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08855064
...
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@@ -659,6 +659,40 @@ FROM orders
GROUP
BY
date
(
created_at
)
```
### Total of grouped items
To get the total of grouped items on a single query call
`count`
after the
`group`
.
```
ruby
Order
.
group
(
:status
).
count
# => { 'awaiting_approval' => 7, 'paid' => 12 }
```
The SQL that would be executed would be something like this:
```
sql
SELECT
COUNT
(
*
)
AS
count_all
,
status
AS
status
FROM
"orders"
GROUP
BY
status
```
It is possible to do this count with multiple values, to do this only add the
other column to
`group`
.
```
ruby
Order
.
group
(
:status
,
:delivery_method
).
count
# => { ['awaiting_approval', 'regular'] => 5, ['awaiting_approval', 'fast'] => 2, ['paid', 'regular'] => 2, ['paid', 'fast'] => 10 }
```
The SQL that would be executed would be something like this:
```
sql
SELECT
COUNT
(
*
)
AS
count_all
,
status
AS
status
,
delivery_method
AS
delivery_method
FROM
"orders"
GROUP
BY
status
,
delivery_method
```
Having
------
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...
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