Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/4046#discussion_r120749951
--- Diff: docs/dev/table/sql.md ---
@@ -22,20 +22,22 @@ specific language governing permissions and limitations
under the License.
-->
-SQL queries are specified using the `sql()` method of the
`TableEnvironment`. The method returns the result of the SQL query as a `Table`
which can be converted into a `DataSet` or `DataStream`, used in subsequent
Table API queries, or written to a `TableSink` (see [Writing Tables to External
Sinks](#writing-tables-to-external-sinks)). SQL and Table API queries can
seamlessly mixed and are holistically optimized and translated into a single
DataStream or DataSet program.
+Flink supports specifying DataStream or DataSet programs with SQL queries
using the `sql()` method of the `TableEnvironment`. The method returns the
result of the SQL query as a `Table`. A `Table` can be used in subsequent SQL /
Table API queries, be converted into a `DataSet` or `DataStream`, or written to
a `TableSink` (see [Writing Tables to External
Sinks](common.html#emit-to-a-tablesink)). SQL and Table API queries can
seamlessly mixed and are holistically optimized and translated into a single
program.
-A `Table`, `DataSet`, `DataStream`, or external `TableSource` must be
registered in the `TableEnvironment` in order to be accessible by a SQL query
(see [Registering Tables](#registering-tables)). For convenience
`Table.toString()` will automatically register an unique table name under the
`Table`'s `TableEnvironment` and return the table name. So it allows to call
SQL directly on tables in a string concatenation (see examples below).
+Before using data in a SQL query, the data source(s) must first be
registered in the `TableEnvironment` (see see [Registering
Tables](common.html#register-a-table-in-the-catalog)). Possible data sources
include Tables, DataSets, DataStreams, and external TableSources.
Alternatively, users can also register external catalogs in the
`TableEnvironment` to specify the location of the data sources.
--- End diff --
Add a link to
http://localhost:4000/dev/table/common.html#register-an-external-catalog
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