hive> explain select b.name, c.name from log a > left outer join (select uid, name from user) b on (a.uid=b.uid) > left outer join user c on (a.uid=c.uid); OK STAGE DEPENDENCIES: Stage-5 is a root stage Stage-4 depends on stages: Stage-5 Stage-0 depends on stages: Stage-4 STAGE PLANS: Stage: Stage-5 Map Reduce Local Work Alias -> Map Local Tables: b:user Fetch Operator limit: -1 c Fetch Operator limit: -1 Alias -> Map Local Operator Tree: b:user TableScan alias: user Statistics: Num rows: 1 Data size: 7 Basic stats: COMPLETE Column stats: NONE Select Operator expressions: uid (type: string), name (type: string) outputColumnNames: _col0, _col1 Statistics: Num rows: 1 Data size: 7 Basic stats: COMPLETE Column stats: NONE HashTable Sink Operator keys: 0 uid (type: string) 1 _col0 (type: string) 2 uid (type: string) c TableScan alias: c Statistics: Num rows: 1 Data size: 7 Basic stats: COMPLETE Column stats: NONE HashTable Sink Operator keys: 0 uid (type: string) 1 _col0 (type: string) 2 uid (type: string) Stage: Stage-4 Map Reduce Map Operator Tree: TableScan alias: a Statistics: Num rows: 1 Data size: 3 Basic stats: COMPLETE Column stats: NONE Map Join Operator condition map: Left Outer Join0 to 1 Left Outer Join0 to 2 keys: 0 uid (type: string) 1 _col0 (type: string) 2 uid (type: string) outputColumnNames: _col6, _col8 Statistics: Num rows: 2 Data size: 6 Basic stats: COMPLETE Column stats: NONE Select Operator expressions: _col6 (type: string), _col8 (type: string) outputColumnNames: _col0, _col1 Statistics: Num rows: 2 Data size: 6 Basic stats: COMPLETE Column stats: NONE File Output Operator compressed: false Statistics: Num rows: 2 Data size: 6 Basic stats: COMPLETE Column stats: NONE table: input format: org.apache.hadoop.mapred.TextInputFormat output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe Local Work: Map Reduce Local Work Stage: Stage-0 Fetch Operator limit: -1 Processor Tree: ListSink Time taken: 0.201 seconds, Fetched: 75 row(s)