org.apache.flink.table.api

Interface GroupedTable

@PublicEvolving
public interface GroupedTable

A table that has been grouped on a set of grouping keys.

Method Summary

Modifier and Type	Method and Description
AggregatedTable	aggregate(Expression aggregateFunction) Performs an aggregate operation with an aggregate function.
FlatAggregateTable	flatAggregate(Expression tableAggFunction) Performs a flatAggregate operation on a grouped table.
Table	select(Expression... fields) Performs a selection operation on a grouped table.

Method Detail

select

Table select(Expression... fields)

Performs a selection operation on a grouped table. Similar to an SQL SELECT statement. The field expressions can contain complex expressions and aggregations.

Example:

 tab.groupBy($("key")).select($("key"), $("value").avg().plus(" The average").as("average"));
 

Scala Example:

 tab.groupBy($"key").select($"key", $"value".avg + " The average" as "average")
 

aggregate

AggregatedTable aggregate(Expression aggregateFunction)

Performs an aggregate operation with an aggregate function. You have to close the aggregate(Expression) with a select statement. The output will be flattened if the output type is a composite type.

Example:

 tableEnv.createTemporarySystemFunction("aggFunc", MyAggregateFunction.class);
 tab.groupBy($("key"))
   .aggregate(call("aggFunc", $("a"), $("b")).as("f0", "f1", "f2"))
   .select($("key"), $("f0"), $("f1"));
 

Scala Example:

 val aggFunc = new MyAggregateFunction
 table.groupBy($"key")
   .aggregate(aggFunc($"a", $"b") as ("f0", "f1", "f2"))
   .select($"key", $"f0", $"f1")
 

flatAggregate

FlatAggregateTable flatAggregate(Expression tableAggFunction)

Performs a flatAggregate operation on a grouped table. FlatAggregate takes a TableAggregateFunction which returns multiple rows. Use a selection after flatAggregate.

Example:

 tableEnv.createTemporarySystemFunction("tableAggFunc", MyTableAggregateFunction.class);
 tab.groupBy($("key"))
   .flatAggregate(call("tableAggFunc", $("a"), $("b")).as("x", "y", "z"))
   .select($("key"), $("x"), $("y"), $("z"));
 

Scala Example:

 val tableAggFunc: TableAggregateFunction = new MyTableAggregateFunction
 tab.groupBy($"key")
   .flatAggregate(tableAggFunc($"a", $"b") as ("x", "y", "z"))
   .select($"key", $"x", $"y", $"z")