Hm - I noticed several of these say `wikistats_sampled`. Not sure if that is another table you meant to create or if the name should be changed to `wikistats_sample_cached`. Also, when I run this I get an exception:

blinkdb> select dt, approx_sum(page_views) from wikistats_sample_cached group by dt;
...
org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException: Exactly one argument is expected.
	at org.apache.hadoop.hive.ql.udf.approx.ApproxUDAFSum.getEvaluator(ApproxUDAFSum.java:59)
	at org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver.getEvaluator(AbstractGenericUDAFResolver.java:47)
	at org.apache.hadoop.hive.ql.exec.FunctionRegistry.getGenericUDAFEvaluator(FunctionRegistry.java:784)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.getGenericUDAFEvaluator(SemanticAnalyzer.java:2464)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genGroupByPlanMapGroupByOperator(SemanticAnalyzer.java:2904)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genGroupByPlanMapAggr1MR(SemanticAnalyzer.java:3704)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genBodyPlan(SemanticAnalyzer.java:6183)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.genPlan(SemanticAnalyzer.java:6820)
	at shark.parse.SharkSemanticAnalyzer.analyzeInternal(SharkSemanticAnalyzer.scala:150)
	at org.apache.hadoop.hive.ql.parse.BaseSemanticAnalyzer.analyze(BaseSemanticAnalyzer.java:244)