<?xml version="1.0" encoding="utf-8" ?><rss version="2.0"><channel><title><![CDATA[我的学习成长日记]]></title><description><![CDATA[]]></description><link>https://blog.youkuaiyun.com/OnlyQi</link><language>zh-cn</language><generator>https://blog.youkuaiyun.com/</generator><copyright><![CDATA[Copyright &copy; OnlyQi]]></copyright><item><title><![CDATA[Hierarchical Queries in Oracle]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/120493951</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/120493951</guid><author>OnlyQi</author><pubDate>Sun, 26 Sep 2021 18:27:57 +0800</pubDate><description><![CDATA[有一些表存在层级关系，例如Oracle的示例表hr.employees：

LAST_NAME
			EMPLOYEE_ID
			MANAGER_ID
		King
			100
			-
		Kochhar
			101
			100
		De Haan
			102
			100
		Hunold
			103
			102
		Ernst
			104
			103
		

可以看到每个员工有自己的manager，从而形成类似这样的层级关系：



King是最大的领导，因此他就是root，下面有.]]></description><category></category></item><item><title><![CDATA[SQL left/right join]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/120361501</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/120361501</guid><author>OnlyQi</author><pubDate>Sat, 18 Sep 2021 09:57:09 +0800</pubDate><description><![CDATA[记一下left/right join中，使用不同条件的不同结果。


测试表：
create table yan_test1 ( id int,test VARCHAR(20))
create table yan_test2 ( id int,test VARCHAR(20))

Query1

select a.*, b.*
from yan_test1 a, yan_test2 b
where a.id = b.id (+)
------------------------
1 test_string ]]></description><category></category></item><item><title><![CDATA[Oracle中的物化视图]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/115467279</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/115467279</guid><author>OnlyQi</author><pubDate>Tue, 06 Apr 2021 20:55:35 +0800</pubDate><description><![CDATA[原文

A materialized view is a replica of a target master from a single point in time. The master can be either a master table at a master site or a master materialized view at a materialized view site.A materialized view can be either read-only, updatable..]]></description><category></category></item><item><title><![CDATA[Oracle中的表概览]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/113511501</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/113511501</guid><author>OnlyQi</author><pubDate>Mon, 01 Feb 2021 19:59:56 +0800</pubDate><description><![CDATA[表是Oracle数据库中数据组织的基本单元。Oracle支持多种表，从不同的角度可划分为多种类型：

关系型表(Relational tables)和对象型表(Object tables)

关系型表是最常见的表类型。关系型表是一张二维表，其中“关系”是指不同字段值组合在一起构成的关系，以及表与表之间的关系(也就是外键)。

熟悉Java等面向对象语言的同学应该对“对象”这个概念很熟悉。对象型表是指表中的数据支持封装，继承等面向对象特性的那些表。

堆表(heap-organized table)和索引组织]]></description><category></category></item><item><title><![CDATA[Oracle数据库架构]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/113436730</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/113436730</guid><author>OnlyQi</author><pubDate>Mon, 01 Feb 2021 11:39:52 +0800</pubDate><description><![CDATA[参考文档



多租户架构

Instance

由内存中的SGA和一系列的进程组成。

CDB

由control file，online redo files and data files组成。

instance + CDB则组成了一个Oracle database。

PDBs

是由用户创建的，物理上由一个或多个data files组成。由于PDBs只有data files，显然PDBs需要“plug”到CDB才能使用。PDBs也可以被unplugged，unplugged后的PDBs包含一个或.]]></description><category></category></item><item><title><![CDATA[Oracle中的row结构]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/113401302</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/113401302</guid><author>OnlyQi</author><pubDate>Fri, 29 Jan 2021 18:20:01 +0800</pubDate><description><![CDATA[参考文档

Oracle中一行数据是由一个或多个row piece组成的。如果一整行数据可以被放入一个单独的data block中，则这一整行数据就是一个row piece。如果由于一行数据太长，需要将一行数据放入多个data block中，则将这一整行数据拆分成多个row piece，一个row piece放入一个data block。一个data block通常也只会存储一行数据的一个row piece。

每一行数据在data block header的row directory中都有一个slot，记]]></description><category></category></item><item><title><![CDATA[记录几个Oracle官方文档]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/113389210</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/113389210</guid><author>OnlyQi</author><pubDate>Fri, 29 Jan 2021 15:21:34 +0800</pubDate><description><![CDATA[Oracle Database Concepts

SQL Tunning Guide

Database Performance Tunning Guide

Data Warehouse Guide
]]></description><category></category></item><item><title><![CDATA[Pandas中的groupby方法]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112984451</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112984451</guid><author>OnlyQi</author><pubDate>Fri, 22 Jan 2021 15:39:01 +0800</pubDate><description><![CDATA[参考文档

Pandas中的groupby可以分成split-apply-combine来理解:

 1，Split the data into groups

 2，Apply a function to each group independently

 3，Combine the results into a data structure

其中第一步就是由groupby方法实现的。

例如将dataframe按照性别分组。


&gt;&gt;&gt; file.groupby("Se...]]></description><category></category></item><item><title><![CDATA[将数组中的数字按出现次数排序打印]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112969850</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112969850</guid><author>OnlyQi</author><pubDate>Thu, 21 Jan 2021 19:12:33 +0800</pubDate><description><![CDATA[l= [0,1,2,0,2,2,1,1,4]

dic = {}
for v in l: # 统计每个数字出现的次数并存入dictionary，数字本身为key，出现的次数为value。
  if v in dic:
    dic[v] = dic[v] + 1
  else:
    dic[v] = 1

l_new = [None] * len(l) # 生成一个list
for k,v in dic.items(): # 将dictionary中统计的数字放入lis...]]></description><category></category></item><item><title><![CDATA[找出数组中两个元素相加等于10的组合]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112768933</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112768933</guid><author>OnlyQi</author><pubDate>Mon, 18 Jan 2021 12:29:26 +0800</pubDate><description><![CDATA[1，O(N^2) 双重循环:


def get_pair(input_list): # 简单双重循环，结果会有很多重复值。 

    for v1 in input_list: 
        for v2 in input_list:
            if v1 + v2 == 10:
                print(v1, v2)

l = [2,3,5,1,8,9,5,7,4,6,9]
get_pair(l)

--------------------------------]]></description><category></category></item><item><title><![CDATA[Python的进阶话题]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112692633</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112692633</guid><author>OnlyQi</author><pubDate>Sat, 16 Jan 2021 14:19:01 +0800</pubDate><description><![CDATA[1，Closure


def outer_f(x):
    def inner_f(y):
        return x + y
    return inner_f # 注意这里只写函数名，不能带()，因为不是调用，而且把函数的identifier送出去。

test = outer_f(3) # closure的意思是，将outer_f(3)的逻辑和状态作为一个整体封装起来，因此称为closure。
print(test(5))

2，Generator


def f(): # 这个函数称为一]]></description><category></category></item><item><title><![CDATA[用Python访问Elasticsearch]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112647167</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112647167</guid><author>OnlyQi</author><pubDate>Fri, 15 Jan 2021 15:09:58 +0800</pubDate><description><![CDATA[首先，虽然Python提供访问网络资源的module，但是不好用。更常用的是第三方的requests类库：官网

1，在浏览器中输入url：http://localhost:9200/，则会返回如下Elasticsearch的基本信息。


{
  "name" : "ubuntu",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "chev4_PcSg2Lfw_Me1o2xg",
  "version" : {
    "number" : ]]></description><category></category></item><item><title><![CDATA[Python常用类库]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112646603</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112646603</guid><author>OnlyQi</author><pubDate>Fri, 15 Jan 2021 10:36:16 +0800</pubDate><description><![CDATA[官方文档1和官方文档2

1，OS

The os module provides dozens of functions for interacting with the operating system。


&gt;&gt;&gt; import os
&gt;&gt;&gt; os.getcwd() # 其实看起来和命令行操作很像。
'/home/PycharmProjects/pythonProject1'
&gt;&gt;&gt; os.chdir('/home')
&gt;&gt;&gt; o]]></description><category></category></item><item><title><![CDATA[Elasticsearch 简介]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112610020</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112610020</guid><author>OnlyQi</author><pubDate>Thu, 14 Jan 2021 15:14:32 +0800</pubDate><description><![CDATA[Elasticsearch现在在数据处理领域得到了广泛使用。

在Elasticsearch中，数据的逻辑单元称为index(类似数据库中的表)，而其中的数据成为document(类似数据库中的一行数据)。当我们把数据load到Elasticsearch时，例如load一个JSON文件，该文件中的数据会被load到一个index中，且一行JSON数据成为一个document。而每个value需要被自动映射到datatype上，这个过程是Elasticsearch自动完成的，称为dynamic mappin.]]></description><category></category></item><item><title><![CDATA[Python基础(二)]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112505966</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112505966</guid><author>OnlyQi</author><pubDate>Tue, 12 Jan 2021 09:57:47 +0800</pubDate><description><![CDATA[1，Lambda函数

Lambda是一种简洁的表达方式，且只能是一行代码。例如：


def add(x, y):
    return x + y
add(5, 3)

和如下Lambda函数是等效的：


add = lambda x,y:x+y
add(5,3) # 由此可见lambda表达式返回的是一个function
# 甚至等同于下面更为简洁的写法，即不需要给函数命名：
(lambda x, y: x + y)(5, 3)

2，Local and Global Scope

Local sc]]></description><category></category></item><item><title><![CDATA[Oracle的primary key]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112505417</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112505417</guid><author>OnlyQi</author><pubDate>Tue, 12 Jan 2021 08:09:02 +0800</pubDate><description><![CDATA[转载：https://www.oracletutorial.com/oracle-basics/oracle-primary-key/
]]></description><category></category></item><item><title><![CDATA[PL/SQL中的循环控制]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112473680</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112473680</guid><author>OnlyQi</author><pubDate>Mon, 11 Jan 2021 16:27:26 +0800</pubDate><description><![CDATA[参考原文：controlling-the-flow-of-execution

1, For loop

For loop分为numeric and a cursor FOR loop两种：


PROCEDURE display_multiple_years ( -- numeric FOR loop的例子
   start_year_in IN PLS_INTEGER
  ,end_year_in   IN PLS_INTEGER
)
IS
BEGIN
  FOR l_current_year  -- ]]></description><category></category></item><item><title><![CDATA[PL/SQL中的BULK COLLECT/FORALL]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112465441</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112465441</guid><author>OnlyQi</author><pubDate>Mon, 11 Jan 2021 16:05:36 +0800</pubDate><description><![CDATA[本文参考文档：bulk collect and forall

我们通常会在PL/SQL中同时使用PL/SQL和SQL statements。PL/SQL statements are run by the PL/SQL statement executor; SQL statements are run by the SQL statement executor. When the PL/SQL runtime engine encounters a SQL statement, it stops and]]></description><category></category></item><item><title><![CDATA[PL/SQl基础概览]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/112461278</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/112461278</guid><author>OnlyQi</author><pubDate>Mon, 11 Jan 2021 12:32:56 +0800</pubDate><description><![CDATA[本文参考了官方文档：https://www.oracle.com/database/technologies/appdev/plsql.html

PL/SQL的特点：

a，PL/SQL is case-insensitive with regard to identifiers. 通常的做法是关键字大写，变量名等使用小写且用下划线分割。
b，Unless you put double quotation marks around the names of those database objects(t]]></description><category></category></item><item><title><![CDATA[Oracle中的分析函数]]></title><link>https://blog.youkuaiyun.com/OnlyQi/article/details/108985244</link><guid>https://blog.youkuaiyun.com/OnlyQi/article/details/108985244</guid><author>OnlyQi</author><pubDate>Sat, 10 Oct 2020 12:46:50 +0800</pubDate><description><![CDATA[Oracle中的分析函数功能强大，非常方便，因此要重点掌握。现在SQL Server，MySQL也都提供了类似的函数。
1，基本语法

]]></description><category></category></item></channel></rss>