Flink SQL

Query

使用TableEnvironment的sqlQuery()方法指定SQL查询。该方法以表的形式返回SQL查询的结果。表可以用于后续的SQL和表API查询，可以转换为DataSet或DataStream，也可以写入TableSink)。可以无缝地混合SQL和Table API查询，并对其进行整体优化，并将其转换为单个程序。
为了访问SQL查询中的表，必须在TableEnvironment中注册表。可以从TableSource, Table, DataStream, 或 DataSet.注册表。另外，用户还可以在TableEnvironment中注册外部目录，以指定数据源的位置。
为了方便起见，Table.toString()在TableEnvironment中以惟一的名称自动注册表并返回该名称。因此，表对象可以直接内联到SQL查询中(通过字符串连接)，如下面的示例所示。

Flink使用Apache Calcite解析SQL ，它支持标准的ANSI SQL。Flink不支持DDL语句。

操作

扫描，投影，过滤(Scan, Projection, and Filter)

聚合(Aggregations)

GroupBy Aggregation

SELECT a, SUM(b) as d 
FROM Orders 
GROUP BY a

GroupBy Window Aggregation

SELECT user, SUM(amount) 
FROM Orders 
GROUP BY TUMBLE(rowtime, INTERVAL '1' DAY), user

关联(Joins)

集合操作(Set Operations)

Union

SELECT *
FROM (
    (SELECT user FROM Orders WHERE a % 2 = 0)
  UNION
    (SELECT user FROM Orders WHERE b = 0)
)

Union All

SELECT *
FROM (
    (SELECT user FROM Orders WHERE a % 2 = 0)
  UNION ALL
    (SELECT user FROM Orders WHERE b = 0)
)

OrderBy & Limit

流式查询的结果必须主要按升序时间属性排序。支持其他排序属性。
Order By

SELECT * 
FROM Orders 
ORDER BY orderTime

Limit

SELECT * 
ROM Orders 
LIMIT 3

插入(Insert)

INSERT INTO OutputTable
SELECT users, tag
FROM Orders

模式识别(Pattern Recognition)

DDL

Flink的DDL支持尚未完成。
以下示例显示如何指定SQL DDL。

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);

// SQL query with a registered table
// register a table named "Orders"
tableEnv.sqlUpdate("CREATE TABLE Orders (`user` BIGINT, product VARCHAR, amount INT) WITH (...)");
// run a SQL query on the Table and retrieve the result as a new Table
Table result = tableEnv.sqlQuery(
  "SELECT product, amount FROM Orders WHERE product LIKE '%Rubber%'");

// SQL update with a registered table
// register a TableSink
tableEnv.sqlUpdate("CREATE TABLE RubberOrders(product VARCHAR, amount INT) WITH (...)");
// run a SQL update query on the Table and emit the result to the TableSink
tableEnv.sqlUpdate(
  "INSERT INTO RubberOrders SELECT product, amount FROM Orders WHERE product LIKE '%Rubber%'");

创建表

CREATE 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, ...)

删除表

DROP TABLE [IF EXISTS] [catalog_name.][db_name.]table_name