从flink的官方文档，我们知道flink的编程模型分为四层，sql层是最高层的api，Table api是中间层，DataStream/DataSet Api 是核心，stateful Streaming process层是底层实现。

其中，

flink dataset api使用及原理介绍了DataSet Api

flink DataStream API使用及原理介绍了DataStream Api

flink中的时间戳如何使用？---Watermark使用及原理介绍了底层实现的基础Watermark

flink window实例分析介绍了window的概念及使用原理

Flink中的状态与容错介绍了State的概念及checkpoint，savepoint的容错机制

0. 基本概念：

0.1 TableEnvironment

TableEnvironment是Table API和SQL集成的核心概念，它主要负责:

1、在内部目录Catalog中注册一个Table

2、注册一个外部目录Catalog

3、执行SQL查询

4、注册一个用户自定义函数UDF

5、将DataStream或者DataSet转换成Table

6、持有BatchTableEnvironment或者StreamTableEnvironment的引用

/** * The base class for batch and stream TableEnvironments.

*

* <p>The TableEnvironment is a central concept of the Table API and SQL integration. It is

* responsible for:

*

* <ul>

* <li>Registering a Table in the internal catalog</li>

* <li>Registering an external catalog</li>

* <li>Executing SQL queries</li>

* <li>Registering a user-defined scalar function. For the user-defined table and aggregate

* function, use the StreamTableEnvironment or BatchTableEnvironment</li>

* </ul>

*/

0.2 Catalog

Catalog：所有对数据库和表的元数据信息都存放再Flink CataLog内部目录结构中，其存放了flink内部所有与Table相关的元数据信息，包括表结构信息/数据源信息等。

/** * This interface is responsible for reading and writing metadata such as database/table/views/UDFs

* from a registered catalog. It connects a registered catalog and Flink's Table API.

*/

其结构如下：

 0.3 TableSource

在使用Table API时，可以将外部的数据源直接注册成Table数据结构。此结构称之为TableSource

/** * Defines an external table with the schema that is provided by {@link TableSource#getTableSchema}.

*

* <p>The data of a {@link TableSource} is produced as a {@code DataSet} in case of a {@code BatchTableSource}

* or as a {@code DataStream} in case of a {@code StreamTableSource}. The type of ths produced

* {@code DataSet} or {@code DataStream} is specified by the {@link TableSource#getProducedDataType()} method.

*

* <p>By default, the fields of the {@link TableSchema} are implicitly mapped by name to the fields of

* the produced {@link DataType}. An explicit mapping can be defined by implementing the

* {@link DefinedFieldMapping} interface.

*

* @param <T> The return type of the {@link TableSource}.

*/