[GitHub] [spark] huaxingao commented on a change in pull request #28130: [SPARK-31355][SQL][DOCS] Document TABLESAMPLE in SQL Reference

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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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