Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4012#discussion_r119076101
--- Diff: docs/dev/table/common.md ---
@@ -98,374 +89,767 @@ env.execute("Your Query")
</div>
</div>
+**Note:** Table API and SQL queries can be easily integrated with and
embedded into DataStream or DataSet programs. Have a look a the [Integration
with DataStream and DataSet API](#integration-with-datastream-and-dataset-api)
section to learn how DataStreams and DataSets can be converted into Tables and
vice versa.
+
{% top %}
Create a TableEnvironment
-------------------------
-A `Table` is always bound to a specific `TableEnvironment`. It is not
possible to combine Tables of different TableEnvironments.
+The `TableEnvironment` is a central concept of the Table API and SQL
integration. It is responsible for:
+* Registering a `Table` in the internal catalog
+* Registering an external catalog
+* Executing SQL queries
+* Registering a user-defined (scalar, table, or aggregation) function
+* Converting a `DataStream` or `DataSet` into a `Table`
+* Holding a reference to an `ExecutionEnvironment` or
`StreamExecutionEnvironment`
+
+A `Table` is always bound to a specific `TableEnvironment`. It is not
process tables of different TableEnvironments in the same query, e.g., to join
or union them.
+
+A `TableEnvironment` is created by calling the static
`TableEnvironment.getTableEnvironment()` method with a
`StreamExecutionEnvironment` or an `ExecutionEnvironment` and an optional
`TableConfig`. The `TableConfig` can be used to configure the
`TableEnvironment` or to customize the query optimization and translation
process (see [Query Optimization](#query-optimization)).
-**TODO: Extend**
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+// ***************
+// STREAMING QUERY
+// ***************
+StreamExecutionEnvironment sEnv =
StreamExecutionEnvironment.getExecutionEnvironment();
+// Create a TableEnvironment for streaming queries
+StreamTableEnvironment sTableEnv =
TableEnvironment.getTableEnvironment(sEnv);
+
+// ***********
+// BATCH QUERY
+// ***********
+ExecutionEnvironment bEnv = ExecutionEnvironment.getExecutionEnvironment();
+// Create a TableEnvironment for batch queries
+BatchTableEnvironment bTableEnv =
TableEnvironment.getTableEnvironment(bEnv);
+{% endhighlight %}
+</div>
+
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+// ***************
+// STREAMING QUERY
+// ***************
+val sEnv = StreamExecutionEnvironment.getExecutionEnvironment
+// Create a TableEnvironment for streaming queries
+val sTableEnv = TableEnvironment.getTableEnvironment(sEnv)
+
+// ***********
+// BATCH QUERY
+// ***********
+val bEnv = ExecutionEnvironment.getExecutionEnvironment
+// Create a TableEnvironment for batch queries
+val bTableEnv = TableEnvironment.getTableEnvironment(bEnv)
+{% endhighlight %}
+</div>
+</div>
{% top %}
Register a Table in the Catalog
-------------------------------
-`TableEnvironment`s have an internal table catalog to which tables can be
registered with a unique name. After registration, a table can be accessed from
the `TableEnvironment` by its name.
+A `TableEnvironment` has an internal catalog to register tables by name.
Table API or SQL queries can access tables, which are registered in the catalog
by referencing them with their name.
-*Note: `DataSet`s or `DataStream`s can be directly converted into `Table`s
without registering them in the `TableEnvironment`. See [Create a Table from a
DataStream or DataSet](#tbd) for details.
+A `TableEnvironment` allows to register a table from various sources:
+* an existing `Table` object, usually the result of a Table API or SQL
query.
+* a `TableSource`, which accesses external data, such as a file, database,
or messaging system.
+* a `DataStream` or `DataSet` from a DataStream or DataSet program.
+
+Registering a `DataStream` or `DataSet` as a table is discussed in the
[Integration with DataStream and DataSet
API](#integration-with-datastream-and-dataset-api) section.
### Register a Table
-A `Table` that originates from a Table API operation or a SQL query is
registered in a `TableEnvironment` as follows:
+A `Table` is registered in a `TableEnvironment` as follows:
<div class="codetabs" markdown="1">
<div data-lang="java" markdown="1">
{% highlight java %}
-// works for StreamExecutionEnvironment identically
-ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
-BatchTableEnvironment tableEnv = TableEnvironment.getTableEnvironment(env);
+// get a StreamTableEnvironment, works for BatchTableEnvironment
equivalently
+StreamTableEnvironment tableEnv =
TableEnvironment.getTableEnvironment(env);
-// convert a DataSet into a Table
-Table custT = tableEnv
- .toTable(custDs, "name, zipcode")
- .where("zipcode = '12345'")
- .select("name");
+// Table is the result of a simple projection query
+Table projX = tableEnv.scan("X").project(...);
--- End diff --
How about `projX ` -> `projTab`?
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