sunjincheng121 commented on a change in pull request #8087:
[FLINK-12029][table] Add column operations for TableApi
URL: https://github.com/apache/flink/pull/8087#discussion_r276875417
##########
File path: docs/dev/table/functions.md
##########
@@ -5800,3 +5800,284 @@ For Table API, please use `_` for spaces (e.g.,
`DAY_TO_HOUR`).
| | `SQL_TSI_SECOND ` _(SQL-only)_ |
{% top %}
+
+Column Functions
+---------------------------------------
+
+The column functions are used to select or deselect table columns.
+
+| SYNTAX | DESC |
+| :--------------------- | :-------------------------- |
+| columns(...) | select the specified columns |
+| -columns(...) | deselect the columns specified |
+
+The detailed syntax is as follows:
+
+{% highlight text %}
+columnFunction:
+ [-]columns(columnExprs)
+
+columnExprs:
+ columnExpr [, columnExpr]*
+
+columnExpr:
+ columnRef | columnIndex to columnIndex | columnName to columnName
+
+columnRef:
+ columnName(The field name that exists in the table) | columnIndex(a
positive integer starting from 1)
+{% endhighlight %}
+
+The usage of the column function is illustrated in the following table.
(Suppose we have a table with 5 columns: `(a: Int, b: Long, c: String,
d:String, e: String)`):
+
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+
+<table class="table table-bordered">
+ <thead>
+ <tr>
+ <th class="text-left" style="width: 20%">Api</th>
+ <th class="text-center">Usage</th>
+ <th class="text-center">Description</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>
+ columns(*)|*
Review comment:
We should correct all the name for `columns` and `-columns` for this doc.
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