SET EXPLAIN 的 Query Statistics 部分提供关于从外部表加载数据或将数据卸载到外部表的操作的信息。
SET EXPLAIN 输出文件的 Query Statistics 部分中的下列代码提供关于外部表的信息：
下列示例展示一查询，其中的操作是从外部表加载数据并将数据插入到基础表内：
QUERY: (OPTIMIZATION TIMESTAMP: 11-11-2009 12:55:20) ------ insert into items select * from ext_items Estimated Cost: 5 Estimated # of Rows Returned: 68 1) gbasedbt.ext_items: SEQUENTIAL SCAN Query statistics: ----------------- Table map : ---------------------------- Internal name Table name ---------------------------- t1 items type it_count time ---------------------------- xlread 1 00:00.00 type it_count time ---------------------------- xlcnv 67 00:00.00 type table rows_ins time ----------------------------------- insert t1 67 00:00.00
下列示例展示一查询，其中的操作是从基础表读数据并写到外部表指向的文件：
QUERY: (OPTIMIZATION TIMESTAMP: 11-11-2009 12:47:55)
------
select * from orders into external ord_ext
using (datafiles ('disk:/tmp/ord'))
Estimated Cost: 2
Estimated # of Rows Returned: 23
1) gbasedbt.orders: SEQUENTIAL SCAN
Query statistics:
-----------------
Table map :
----------------------------
Internal name Table name
----------------------------
t1 orders
type table rows_prod est_rows rows_scan time est_cost
-------------------------------------------------------------------
scan t1 23 23 23 00:00.00 3
type it_count time
----------------------------
xucnv 23 00:00.00
type it_count time
----------------------------
xuwrite 23 00:00.00