guykhazma commented on a change in pull request #27216: [SPARK-28801][DOC]
Document SELECT statement in SQL Reference (Main page)
URL: https://github.com/apache/spark/pull/27216#discussion_r368427274
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File path: docs/sql-ref-syntax-qry-select.md
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@@ -18,8 +18,119 @@ license: |
See the License for the specific language governing permissions and
limitations under the License.
---
+Spark supports a `SELECT` statement and conforms to the ANSI SQL standard.
Queries are
+used to retrieve result sets from one or more tables. The following section
+describes the overall query syntax and the sub-sections cover different
constructs
+of a query along with examples.
-Spark SQL is a Apache Spark's module for working with structured data.
-This guide is a reference for Structured Query Language (SQL) for Apache
-Spark. This document describes the SQL constructs supported by Spark in detail
-along with usage examples when applicable.
+### Syntax
+{% highlight sql %}
+[ WITH with_query [ , ... ] ]
+SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] }
+ FROM { from_item [ , ...] }
+ [ WHERE boolean_expression ]
+ [ GROUP BY expression [ , ...] ]
+ [ HAVING boolean_expression ]
+ [ ORDER BY { expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [ , ...] }
]
+ [ SORT BY { expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [ , ...] }
]
+ [ CLUSTER BY { expression [ , ...] } ]
+ [ DISTRIBUTE BY { expression [, ...] } ]
+ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]
+ [ WINDOW { named_window [ , WINDOW named_window, ... ] } ]
+ [ LIMIT { ALL | expression } ]
+{% endhighlight %}
+
+### Parameters
+<dl>
+ <dt><code><em>with_query</em></code></dt>
+ <dd>
+ Specifies the common table expressions (CTEs) before the main
<code>SELECT</code> query block.
+ These table expressions are allowed to be referenced later in the main
query. This is useful to abstract
+ out repeated subquery blocks in the main query and improves readability of
the query.
+ </dd>
+ <dt><code><em>hints</em></code></dt>
+ <dd>
+ Hints can be specified to help spark optimizer make better planning
decisions. Currently spark supports hints
+ that influence selection of join strategies and repartitioning of the
data.
+ </dd>
+ <dt><code><em>ALL</em></code></dt>
+ <dd>
+ Select all matching rows from the relation and is enabled by default.
+ </dd>
+ <dt><code><em>DISTINCT</em></code></dt>
+ <dd>
+ Select all matching rows from the relation after removing duplicates in
results.
+ </dd>
+ <dt><code><em>named_expression</em></code></dt>
+ <dd>
+ A expression with an assigned name. In general, it denotes a column
expression.<br><br>
Review comment:
minor: `An expression`
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