Package org.apache.flink.table.api

Interface GroupedTable

  • @PublicEvolving
public interface GroupedTable
    A table that has been grouped on a set of grouping keys.

    • 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")