数据库

《数据库系统概念》：http://pan.baidu.com/s/1hsiEaVE

小李的数据库之旅（上）：http://chuansong.me/n/742733851433

小李的数据库之旅（下）：http://chuansong.me/n/753738551331

1、数据库系统的应用

2、数据库系统的目标

 

How to learn SQL：https://www.quora.com/How-do-I-learn-SQL

Learn the analytic/windowing functions. You probably know SUM() - it's time to learnSUM () OVER ().  Tom Kyte's excellent Expert One-On-One Oracle has a thorough chapter on analytic functions in SQL.  In many cases, entire subqueries can be replaced with cleverly-used analytic functions. Even if you're not using Oracle, many modern RDBMS support analytic functions and his resource is second-to-none. The book is required reading for anyone who works with databases.

Learn what SQL functions are included with your database. Each database offers a set of string, numeric, aggregation, statistical, and analytic functions. One of the ways I became interested in advanced statistics was by reading the Oracle documentation and learning about the statistical functions supplied with the database.

If your database supports it, write some user-defined functions. Even some procedures. User-defined functions are a terrific way to extend the capabilities of your database.

《Expert One-On-One Oracle》：https://wenku.baidu.com/view/23365148cf84b9d528ea7a37.html

3、分析函数

function 子句

partition 子句

order by 子句

windowing 子句

range 窗口

rows 窗口

specifying 窗口

 

SQL OLAP Functions：http://web.cs.ucla.edu/classes/spring03/cs240B/notes/guion1.pdf

4、SQL中的OLAP

交叉表

数据立方体

交叉表和关系表

pivot 子句

 

 

 

 

cube 子句

rollup 子句

grouping 子句

 

 

 

Python实现cube

import itertools

var_list = ['a', 'b', 'c']

for i in range(0, len(var_list)+1):
    for subset in itertools.combinations(var_list, i):
        print subset

()
('a',)
('b',)
('c',)
('a', 'b')
('a', 'c')
('b', 'c')
('a', 'b', 'c')

Java实现cube

import java.util.LinkedHashSet;
import java.util.Set;

import com.google.common.collect.Sets;

public class GuavaCombinations {

    public static void main(String[] args) {
        Set<String> set = new LinkedHashSet<String>();

        set.add("a");
        set.add("b");
        set.add("c");

        Set<Set<String>> powerSet = Sets.powerSet(set);

        for (Set<String> subSet : powerSet) {
            System.out.println(subSet);
        }

    }

}

[]
[a]
[b]
[a, b]
[c]
[a, c]
[b, c]
[a, b, c]

5、OLAP的分类

多维OLAP：Multi-Dimensional OLAP，简称MOLAP

关系OLAP：Relational OLAP，简称ROLAP

混合OLAP：Hybird OLAP，简称HOLAP