-- 注意了需要在sqlyog中执行下面的代码!!!
use hive3;
show tables;alter table hive3.COLUMNS_V2 modify column COMMENT varchar(256) character set utf8;
alter table hive3.TABLE_PARAMS modify column PARAM_VALUE varchar(4000) character set utf8;
alter table hive3.PARTITION_PARAMS modify column PARAM_VALUE varchar(4000) character set utf8 ;
alter table hive3.PARTITION_KEYS modify column PKEY_COMMENT varchar(4000) character set utf8;
alter table hive3.INDEX_PARAMS modify column PARAM_VALUE varchar(4000) character set utf8;
2.授课hql语句
-- 2025-08-11 授课select * from t_usa_covid19;-- 1.根据州进行state 分组统计 统计每个州有多少个县 county
-- select count(county) from t_usa_covid19
-- where count_date="2021-01-28"
-- group by state;select count(county) from t_usa_covid19where count_date="2021-01-28"group by state;-- 想看一下统计的结果是属于哪一个州的
select state,count(county) as county_nums from t_usa_covid19where count_date="2021-01-28"group by state;-- 2.想看一下每个县的死亡病例，很简单 ，刚才的语句添加一个字段就行了？？？？
-- 下面的hql会报错
-- Error while compiling statement: FAILED:
-- SemanticException [Error 10025]: Line 1:42 Expression not in GROUP BY key 'deaths'select state,count(county) as county_nums,deaths from t_usa_covid19where count_date="2021-01-28"group by state;-- 解决方案
select state,count(county) as county_nums,sum(deaths) from t_usa_covid19where count_date="2021-01-28"group by state;--3、having
--统计2021-01-28死亡病例数大于10000的州
--count_date string,-- county string,-- state string,-- fips int,-- cases int,-- deaths intselect state,sum(deaths) from t_usa_covid19
where count_date="2021-01-28" and sum(deaths)>10000
group by state;
-- 结论：where 语句中不能使用聚合函数 语法报错select state,sum(deaths) from t_usa_covid19
where count_date="2021-01-28"
group by state
having sum(deaths)>10000;-- 上面的sql计算了两次，性能不高 ，我们改写sql让它计算一次 性能能提高
select state,sum(deaths) as cnts from t_usa_covid19
where count_date="2021-01-28"
group by state
having cnts>10000;-- order by
-- 4.根据确诊病例数升序，查询返回结果
select * from t_usa_covid19 order by cases;-- 根据确诊病例数降序显示
select * from t_usa_covid19 order by cases desc ;-- 根据死亡病例数倒序排列 ，查询返回加州每个县的结果
select * from t_usa_covid19
where state="California" order by deaths desc;-- 5. 加州返回结果集 从第一行开始 共三行
select * from t_usa_covid19
where count_date="2021-01-28"
and state="California" limit 0,3;-- 分页建议这样写-- 得出结论 数据索引是从0开始的select * from t_usa_covid19
where count_date="2021-01-28"
and state="California" limit 3;select state,sum(deaths) as cnts from t_usa_covid19
where count_date="2021-01-28"
group by state
having cnts >10000
limit 2;--- 2025-08-11 PM
--table1: 员工表
CREATE TABLE employee(id int,name string,deg string,salary int,dept string) row format delimited
fields terminated by ',';--table2:员工家庭住址信息表
CREATE TABLE employee_address (id int,hno string,street string,city string
) row format delimited
fields terminated by ',';--table3:员工联系方式信息表
CREATE TABLE employee_connection (id int,phno string,email string
) row format delimited
fields terminated by ',';select * from liushao.employee;
--加载数据到表中
load data local inpath '/export/data/hivedata/employee.txt' into table liushao.employee;
