Question

I want to use the stack function, described here : https://cwiki.apache.org/Hive/languagemanual-udf.html#LanguageManualUDF-BuiltinTableGeneratingFunctions%2528UDTF%2529

Hive asks me to provide the multiple aliases for the resulting columns (“The number of aliases in the AS clause does not match the number of colums output by the UDTF, expected 3 aliases but got 1”).

What’s the syntax to provide multiple aliases ?

Answer 1

Syntax is the following :

SELECT stack(n, col1, col2, ..., colk) AS (alias1, alias2, ...) FROM myTable;

Working with LATERAL VIEW, syntax is the following :

SELECT a, b, alias1, alias2... FROM myTable
    LATERAL VIEW stack(n, col1, col2, ..., colk) tableAlias AS alias1, alias2, ... ;