1 创建测试用表

1）建大表、小表和 JOIN 后表的语句

// 创建大表
create table bigtable(id bigint, t bigint, uid string, keyword string, 
url_rank int, click_num int, click_url string) row format delimited 
fields terminated by '\t';

// 创建小表
create table smalltable(id bigint, t bigint, uid string, keyword string, 
url_rank int, click_num int, click_url string) row format delimited 
fields terminated by '\t';

// 创建 JOIN 后表
create table jointable(id bigint, t bigint, uid string, keyword string, 
url_rank int, click_num int, click_url string) row format delimited 
fields terminated by '\t';

2）分别向大表和小表中导入数据

hive (default)> load data local inpath '/opt/module/data/bigtable' into 
table bigtable;
hive (default)> load data local inpath '/opt/module/data/smalltable' into 
table smalltable;

2 基本语法

EXPLAIN [EXTENDED | DEPENDENCY | AUTHORIZATION] query-sql

3 案例实操

1）查看下面这条语句的执行计划

hive (default)> explain select * from bigtable;
hive (default)> explain select click_url, count(*) ct from bigtable group 
by click_url;

2）查看详细执行计划

hive (default)> explain extended select * from bigtable;
hive (default)> explain extended select click_url, count(*) ct from 
bigtable group by click_url;