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The following commit(s) were added to refs/heads/branch-3.0 by this push: new 471f0df [SPARK-31355][SQL][DOCS] Document TABLESAMPLE in SQL Reference 471f0df is described below commit 471f0df08b9b59fe739b3081bb8f923a3097a97d Author: Huaxin Gao <huax...@us.ibm.com> AuthorDate: Thu Apr 9 19:39:34 2020 -0500 [SPARK-31355][SQL][DOCS] Document TABLESAMPLE in SQL Reference ### What changes were proposed in this pull request? Document TABLESAMPLE in SQL Reference ### Why are the changes needed? To make SQL Reference complete ### Does this PR introduce any user-facing change? Yes <img width="1049" alt="Screen Shot 2020-04-06 at 10 23 52 PM" src="https://user-images.githubusercontent.com/13592258/78633123-96749f00-7855-11ea-9509-b7ee21da7fbd.png"> <img width="1050" alt="Screen Shot 2020-04-06 at 10 24 26 PM" src="https://user-images.githubusercontent.com/13592258/78633130-98d6f900-7855-11ea-8675-fd4b6163dfb6.png"> ### How was this patch tested? Manually build and check. Closes #28130 from huaxingao/sampling. Authored-by: Huaxin Gao <huax...@us.ibm.com> Signed-off-by: Sean Owen <sro...@gmail.com> (cherry picked from commit f69b0ef25df744f83c57c50735e8db9f6802e98c) Signed-off-by: Sean Owen <sro...@gmail.com> --- docs/_data/menu-sql.yaml | 2 + docs/sql-ref-syntax-qry-sampling.md | 74 ++++++++++++++++++++++++++++++++++++- docs/sql-ref-syntax-qry-select.md | 1 + 3 files changed, 76 insertions(+), 1 deletion(-) diff --git a/docs/_data/menu-sql.yaml b/docs/_data/menu-sql.yaml index 6f300e2..225450b 100644 --- a/docs/_data/menu-sql.yaml +++ b/docs/_data/menu-sql.yaml @@ -158,6 +158,8 @@ url: sql-ref-syntax-qry-select-hints.html - text: Set Operators url: sql-ref-syntax-qry-select-setops.html + - text: TABLESAMPLE + url: sql-ref-syntax-qry-sampling.html - text: EXPLAIN url: sql-ref-syntax-qry-explain.html - text: Auxiliary Statements diff --git a/docs/sql-ref-syntax-qry-sampling.md b/docs/sql-ref-syntax-qry-sampling.md index a5efb36..061f21c 100644 --- a/docs/sql-ref-syntax-qry-sampling.md +++ b/docs/sql-ref-syntax-qry-sampling.md @@ -19,4 +19,76 @@ 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. + +### Syntax + +{% highlight sql %} + TABLESAMPLE ((integer_expression | decimal_expression) PERCENT) + | TABLESAMPLE (integer_expression ROWS) + | TABLESAMPLE (BUCKET integer_expression OUT OF integer_expression) +{% endhighlight %} + +### Examples + +{% highlight sql %} +SELECT * FROM test; + +--+----+ + |id|name| + +--+----+ + | 5|Alex| + | 8|Lucy| + | 2|Mary| + | 4|Fred| + | 1|Lisa| + | 9|Eric| + |10|Adam| + | 6|Mark| + | 7|Lily| + | 3|Evan| + +--+----+ + +SELECT * FROM test TABLESAMPLE (50 PERCENT); + +--+----+ + |id|name| + +--+----+ + | 5|Alex| + | 2|Mary| + | 4|Fred| + | 9|Eric| + |10|Adam| + | 3|Evan| + +--+----+ + +SELECT * FROM test TABLESAMPLE (5 ROWS); + +--+----+ + |id|name| + +--+----+ + | 5|Alex| + | 8|Lucy| + | 2|Mary| + | 4|Fred| + | 1|Lisa| + +--+----+ + +SELECT * FROM test TABLESAMPLE (BUCKET 4 OUT OF 10); + +--+----+ + |id|name| + +--+----+ + | 8|Lucy| + | 2|Mary| + | 9|Eric| + | 6|Mark| + +--+----+ +{% endhighlight %} + +### Related Statement + + * [SELECT](sql-ref-syntax-qry-select.html) \ No newline at end of file diff --git a/docs/sql-ref-syntax-qry-select.md b/docs/sql-ref-syntax-qry-select.md index 420cf1f..17c1411 100644 --- a/docs/sql-ref-syntax-qry-select.md +++ b/docs/sql-ref-syntax-qry-select.md @@ -150,4 +150,5 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] } - [CLUSTER BY Clause](sql-ref-syntax-qry-select-clusterby.html) - [DISTRIBUTE BY Clause](sql-ref-syntax-qry-select-distribute-by.html) - [LIMIT Clause](sql-ref-syntax-qry-select-limit.html) +- [TABLESAMPLE](sql-ref-syntax-qry-sampling.html) - [SET Operators](sql-ref-syntax-qry-select-setops.html) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@spark.apache.org For additional commands, e-mail: commits-h...@spark.apache.org