danny0405 commented on a change in pull request #9366: [FLINK-13359][docs] Add documentation for DDL introduction URL: https://github.com/apache/flink/pull/9366#discussion_r311835114
########## File path: docs/dev/table/ddl.md ########## @@ -0,0 +1,230 @@ +--- +title: "DDL" +nav-parent_id: tableapi +nav-pos: 0 +--- +<!-- +Licensed to the Apache Software Foundation (ASF) under one +or more contributor license agreements. See the NOTICE file +distributed with this work for additional information +regarding copyright ownership. The ASF licenses this file +to you under the Apache License, Version 2.0 (the +"License"); you may not use this file except in compliance +with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, +software distributed under the License is distributed on an +"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +KIND, either express or implied. See the License for the +specific language governing permissions and limitations +under the License. +--> + +The Table API and SQL are integrated in a joint API. The central concept of this API is a `Table` which serves as input and output of queries. This document shows all the DDL grammar Flink support, how to register a `Table`(or view) through DDL, how to drop a `Table`(or view) through DDL. + +* This will be replaced by the TOC +{:toc} + +Create Table +--------------------------------------- +{% highlight sql %} +CREATE [OR REPLACE] TABLE [catalog_name.][db_name.]table_name + [(col_name1 col_type1 [COMMENT col_comment1], ...)] + [COMMENT table_comment] + [PARTITIONED BY (col_name1, col_name2, ...)] + [WITH (key1=val1, key2=val2, ...)] +{% endhighlight %} + +Create a table with the given table properties. If a table with the same name already exists in the database, an exception is thrown except that *IF NOT EXIST* is declared. + +**OR REPLACE** + +If a table with the same name already exists in the database, replace it if this is declared. **Notes:** The OR REPLACE option is always false now. + +**PARTITIONED BY** + +Partition the created table by the specified columns. A directory is created for each partition. + +**WITH OPTIONS** + +Table properties used to create a table source/sink. The properties are usually used to find and create the underlying connector. **Notes:** the key and value of expression `key1=val1` should both be string literal. + +**Examples**: +{% highlight sql %} +-- CREATE a partitioned CSV table using the CREATE TABLE syntax. +create table csv_table ( + f0 int, + f1 bigint, + f2 string +) +COMMENT 'This is a csv table.' +PARTITIONED BY(f0) +WITH ( + 'connector.type' = 'filesystem', + 'format.type' = 'csv', + 'connector.path' = 'path1' + 'format.fields.0.name' = 'f0', + 'format.fields.0.type' = 'INT', + 'format.fields.1.name' = 'f1', + 'format.fields.1.type' = 'BIGINT', + 'format.fields.2.name' = 'f2', + 'format.fields.2.type' = 'STRING', +); + +-- CREATE a Kafka table start from the earliest offset(as table source) and append mode(as table sink). +create table kafka_table ( + f0 int, + f1 bigint, + f2 string +) with ( + 'connector.type' = 'kafka', + 'update-mode' = 'append', + 'connector.topic' = 'topic_name', + 'connector.startup-mode' = 'earliest-offset', + 'connector.properties.0.key' = 'props-key0', + 'connector.properties.0.value' = 'props-val0', + 'format.fields.0.name' = 'f0', + 'format.fields.0.type' = 'INT', + 'format.fields.1.name' = 'f1', + 'format.fields.1.type' = 'BIGINT', + 'format.fields.2.name' = 'f2', + 'format.fields.2.type' = 'STRING' +); + +-- CREATE a Elasticsearch table. +create table kafka_table ( + f0 int, + f1 bigint, + f2 string +) with ( + 'connector.type' = 'elasticsearch', + 'update-mode' = 'append', + 'connector.hosts.0.hostname' = 'host_name', + 'connector.hosts.0.port' = '9092', + 'connector.hosts.0.protocal' = 'http', + 'connector.index' = 'index_name', + 'connector.document-type' = 'type_name', + 'format.fields.0.name' = 'f0', + 'format.fields.0.type' = 'INT', + 'format.fields.1.name' = 'f1', + 'format.fields.1.type' = 'BIGINT', + 'format.fields.2.name' = 'f2', + 'format.fields.2.type' = 'STRING' +); +{% endhighlight %} + +{% top %} + +Drop Table +--------------------------------------- +{% highlight sql %} +DROP TABLE [IF EXISTS] [catalog_name.][db_name.]table_name +{% endhighlight %} + +Drop a table with the given table name. If the table to drop does not exist, an exception is thrown. + +**IF EXISTS** + +If the table does not exist, nothing happens. + +{% top %} + +Create View +--------------------------------------- +{% highlight sql %} +CREATE [OR REPLACE] VIEW [catalog_name.][db_name.]view_name +[COMMENT view_comment] +AS +select_statement +{% endhighlight %} + +Define a logical view on a sql query which may be from multiple tables or views. + +**OR REPLACE** + +If the view does not exist, CREATE OR REPLACE VIEW is equivalent to CREATE VIEW. If the view does exist, CREATE OR REPLACE VIEW is equivalent to ALTER VIEW. **Notes:** The OR REPLACE option is always false now. + +**AS select_statement** + +A SELECT statement that defines the view. The statement can select from base tables or the other views. + +**Examples**: +{% highlight sql %} +-- Create a view view_deptDetails in database1. The view definition is recorded in the specified catalog and database. +CREATE VIEW catalog1.database1.view1 + AS SELECT * FROM company JOIN dept ON company.dept_id = dept.id; + +-- Create or replace a view from a persistent view with an extra filter +CREATE OR REPLACE VIEW view2 + AS SELECT * FROM catalog1.database1.view1 WHERE loc = 'Shanghai'; + +-- Access the base tables through the view +SELECT * FROM view2; + +-- Drop the view1, view2. +DROP VIEW catalog1.database1.view1; +DROP VIEW IF EXISTS view2; +{% endhighlight %} + +{% top %} + +Execute DDLs from Table Environment +--------------------------------------- +<div class="codetabs" markdown="1"> +<div data-lang="java" markdown="1"> +{% highlight java %} +// for batch programs use ExecutionEnvironment instead of StreamExecutionEnvironment +StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment(); + +// create a TableEnvironment +// for batch programs use BatchTableEnvironment instead of StreamTableEnvironment +StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env); + +// register a Table +tableEnv.sqlUpdate("create table table_name ...") + +{% endhighlight %} +</div> + +<div data-lang="scala" markdown="1"> +{% highlight scala %} +// for batch programs use ExecutionEnvironment instead of StreamExecutionEnvironment +val env = StreamExecutionEnvironment.getExecutionEnvironment + +// create a TableEnvironment +val tableEnv = StreamTableEnvironment.create(env) + +// register a Table +tableEnv.sqlUpdate(""create table table_name ..."") + +{% endhighlight %} +</div> + +<div data-lang="python" markdown="1"> +{% highlight python %} +# for batch programs use ExecutionEnvironment instead of StreamExecutionEnvironment +env = StreamExecutionEnvironment.get_execution_environment() + +# create a TableEnvironment +table_env = StreamTableEnvironment.create(env) + +# register a Table +table_env.sql_update("create table table_name ...") + +{% endhighlight %} +</div> +</div> + +**Notes:** The table name can be two format: 1. `catalog_name.db_name.table_name` 2. `table_name`; For `catalog_name.db_name.table_name`, the table would be registered into metastore with catalog named "catalog_name" and database named "db_name", for `table_name`, the table would be registered into the current catalog and database of the execution table environment. 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