mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-17 05:03:20 +00:00
cd14f9ebcb
* split up select.md * array-join.md basic refactoring * distinct.md basic refactoring * format.md basic refactoring * from.md basic refactoring * group-by.md basic refactoring * having.md basic refactoring * additional index.md refactoring * into-outfile.md basic refactoring * join.md basic refactoring * limit.md basic refactoring * limit-by.md basic refactoring * order-by.md basic refactoring * prewhere.md basic refactoring * adjust operators/index.md links * adjust sample.md links * adjust more links * adjust operatots links * fix some links * adjust aggregate function article titles * basic refactor of remaining select clauses * absolute paths in make_links.sh * run make_links.sh * remove old select.md locations * translate docs/es * translate docs/fr * translate docs/fa * remove old operators.md location * change operators.md links * adjust links in docs/es * adjust links in docs/es * minor texts adjustments * wip * update machine translations to use new links * fix changelog * es build fixes * get rid of some select.md links * temporary adjust ru links * temporary adjust more ru links * improve curly brace handling * adjust ru as well * fa build fix * ru link fixes * zh link fixes * temporary disable part of anchor checks
81 lines
2.0 KiB
Markdown
81 lines
2.0 KiB
Markdown
---
|
|
machine_translated: true
|
|
machine_translated_rev: 72537a2d527c63c07aa5d2361a8829f3895cf2bd
|
|
---
|
|
|
|
# AVEC la Clause {#with-clause}
|
|
|
|
Cette section prend en charge les Expressions de Table courantes ([CTE](https://en.wikipedia.org/wiki/Hierarchical_and_recursive_queries_in_SQL)), de sorte que les résultats de `WITH` la clause peut être utilisé à l'intérieur `SELECT` clause.
|
|
|
|
## Limitation {#limitations}
|
|
|
|
1. Les requêtes récursives ne sont pas prises en charge.
|
|
2. Lorsque la sous-requête est utilisée à l'intérieur avec section, son résultat doit être scalaire avec exactement une ligne.
|
|
3. Les résultats d'Expression ne sont pas disponibles dans les sous-requêtes.
|
|
|
|
## Exemple {#examples}
|
|
|
|
**Exemple 1:** Utilisation d'une expression constante comme “variable”
|
|
|
|
``` sql
|
|
WITH '2019-08-01 15:23:00' as ts_upper_bound
|
|
SELECT *
|
|
FROM hits
|
|
WHERE
|
|
EventDate = toDate(ts_upper_bound) AND
|
|
EventTime <= ts_upper_bound
|
|
```
|
|
|
|
**Exemple 2:** De les expulser, somme(octets) résultat de l'expression de clause SELECT de la liste de colonnes
|
|
|
|
``` sql
|
|
WITH sum(bytes) as s
|
|
SELECT
|
|
formatReadableSize(s),
|
|
table
|
|
FROM system.parts
|
|
GROUP BY table
|
|
ORDER BY s
|
|
```
|
|
|
|
**Exemple 3:** Utilisation des résultats de la sous-requête scalaire
|
|
|
|
``` sql
|
|
/* this example would return TOP 10 of most huge tables */
|
|
WITH
|
|
(
|
|
SELECT sum(bytes)
|
|
FROM system.parts
|
|
WHERE active
|
|
) AS total_disk_usage
|
|
SELECT
|
|
(sum(bytes) / total_disk_usage) * 100 AS table_disk_usage,
|
|
table
|
|
FROM system.parts
|
|
GROUP BY table
|
|
ORDER BY table_disk_usage DESC
|
|
LIMIT 10
|
|
```
|
|
|
|
**Exemple 4:** Réutilisation de l'expression dans la sous-requête
|
|
|
|
Comme solution de contournement pour la limitation actuelle de l'utilisation de l'expression dans les sous-requêtes, Vous pouvez la dupliquer.
|
|
|
|
``` sql
|
|
WITH ['hello'] AS hello
|
|
SELECT
|
|
hello,
|
|
*
|
|
FROM
|
|
(
|
|
WITH ['hello'] AS hello
|
|
SELECT hello
|
|
)
|
|
```
|
|
|
|
``` text
|
|
┌─hello─────┬─hello─────┐
|
|
│ ['hello'] │ ['hello'] │
|
|
└───────────┴───────────┘
|
|
```
|