Hive的CTE 公共表达式

目录

1.语法

[2. 使用场景](#2. 使用场景)

select语句

[chaining CTEs 链式](#chaining CTEs 链式)

union语句

[insert into 语句](#insert into 语句)

[create table as 语句](#create table as 语句)

前言

Common Table Expressions(CTE):公共表达式是一个临时的结果集,该结果集是从with子句中指定的查询派生而来的,紧跟在select 或 insert关键字之前。CTE可以在 select,insert, create table as select 等语句中使用。

1.语法

sql 复制代码
[wtih CommonTableExpression]
select
        column1,
        column2, ...
from table 
[where 条件] 
[group by column]
[order by column] 
[cluster by column| [distribute by column] [sort by column] 
[limit [offset,] rows];

2. 使用场景

select语句

sql 复制代码
with tmp as (
    select
        oid,
        uid,
        otime,
        date_format(otime, 'yyyy-MM') as dt,
        oamount,
        ---计算rk的目的是为了获取记录中的第一条
        row_number() over (partition by uid,date_format(otime, 'yyyy-MM') order by otime) rk
    from t_order
)
 select
    uid,
    --每个用户一月份的订单数
    sum(if(dt = '2018-01', 1, 0)) as  m1_count,
    --每个用户二月份的订单数
    sum(if(dt = '2018-02', 1, 0)) as  m2_count
from tmp
 group by uid
 having m1_count >0 and m2_count=0;

chaining CTEs 链式

sql 复制代码
with tmp1 as (
    select
        oid,
        uid,
        otime,
        date_format(otime, 'yyyy-MM') as dt,
        oamount,
        ---计算rk的目的是为了获取记录中的第一条
        row_number() over (partition by uid,date_format(otime, 'yyyy-MM') order by otime) as rk
    from t_order
),
     tmp2 as
         (select
              uid,
              --每个用户一月份的订单数
              sum(if(dt = '2018-01', 1, 0)) as m1_count,
              --每个用户二月份的订单数
              sum(if(dt = '2018-02', 1, 0)) as m2_count
          from tmp1
          group by uid
          having m1_count > 0
             and m2_count = 0)
select * from tmp2 limit 1;

union语句

sql 复制代码
with q1 as (select * from student where num = 95002),
     q2 as (select * from student where num = 95004)
select * from q1 union all select * from q2;

insert into 语句

sql 复制代码
with tmp1 as (
    select
        oid,
        uid,
        otime,
        date_format(otime, 'yyyy-MM') as dt,
        oamount,
        ---计算rk的目的是为了获取记录中的第一条
        row_number() over (partition by uid,date_format(otime, 'yyyy-MM') order by otime) as rk
    from t_order
),
     tmp2 as
         (select
              uid,
              --每个用户一月份的订单数
              sum(if(dt = '2018-01', 1, 0)) as m1_count,
              --每个用户二月份的订单数
              sum(if(dt = '2018-02', 1, 0)) as m2_count
          from tmp1
          group by uid
          having m1_count > 0
             and m2_count = 0)

insert into tmp3
select * from tmp2 limit 10;

create table as 语句

sql 复制代码
--- 从tmp2 表中取10条数据,基于此创建表tmp3 
create table tmp3 as 
with tmp1 as (
    select
        oid,
        uid,
        otime,
        date_format(otime, 'yyyy-MM') as dt,
        oamount,
        ---计算rk的目的是为了获取记录中的第一条
        row_number() over (partition by uid,date_format(otime, 'yyyy-MM') order by otime) as rk
    from t_order
),
     tmp2 as
         (select
              uid,
              --每个用户一月份的订单数
              sum(if(dt = '2018-01', 1, 0)) as m1_count,
              --每个用户二月份的订单数
              sum(if(dt = '2018-02', 1, 0)) as m2_count
          from tmp1
          group by uid
          having m1_count > 0
             and m2_count = 0)
select * from tmp2 limit 10;
相关推荐
时差9534 小时前
【面试题】Hive 查询:如何查找用户连续三天登录的记录
大数据·数据库·hive·sql·面试·database
苍老流年4 小时前
Hive中各种Join的实现
数据仓库·hive·hadoop
静听山水5 小时前
Hive:UDTF 函数
hive
EDG Zmjjkk6 小时前
Hive 查询(详细实操版)
数据仓库·hive·hadoop
lzhlizihang7 小时前
【Hive sql 面试题】求出各类型专利top 10申请人,以及对应的专利申请数(难)
大数据·hive·sql·面试题
Hsu_kk7 小时前
Hive 查询各类型专利 Top 10 申请人及对应的专利申请数
数据仓库·hive·hadoop
静听山水7 小时前
Hive 的数据存储单元结构
hive
大数据编程之光7 小时前
Hive 查询各类型专利 top10 申请人及专利申请数
大数据·数据仓库·hive·hadoop
杰克逊的日记7 小时前
Hive详解
数据仓库·hive·hadoop
Acrelhuang8 小时前
安科瑞5G基站直流叠光监控系统-安科瑞黄安南
大数据·数据库·数据仓库·物联网