huaxingao commented on a change in pull request #28130:
[SPARK-31355][SQL][DOCS] Document TABLESAMPLE in SQL Reference
URL: https://github.com/apache/spark/pull/28130#discussion_r403827026
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File path: docs/sql-ref-syntax-qry-sampling.md
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@@ -19,4 +19,72 @@ license: |
limitations under the License.
---
-**This page is under construction**
+### Description
+
+The `TABLESAMPLE` statement is used to sample the table. It supports the
following sampling methods:
+- `TABLESAMPLE`(x `ROWS`): Sample the table down to the given number of rows.
+- `TABLESAMPLE`(x `PERCENT`): Sample the table down to the given percentage.
Note that percentages are defined as a number between 0 and 100.
+- `TABLESAMPLE`(`BUCKET` x `OUT OF` y): Sample the table down to a `x` out of
`y` fraction.
+
+Note: `TABLESAMPLE` returns the approximate number of rows or fraction
requested.
Review comment:
Thanks for your comments.
In the related statement, I will cross link ```select``` and
```tablesample```. I am a little hesitate to add tablesample to the ```from
item```. Seems to me, Tablesample is not parallel to Table relation or
InlineTable, the structure is more like this:
```
SELECT ... FROM
Table relation
Tablesample
......
Inlined table
Tablesample
```
Here is how snowflake document this
https://docs.snowflake.com/en/sql-reference/constructs/from.html
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