star-schema | 易学教程

Creating star schema from csv files using Python

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问题 I have 6 dimension tables, all in the form of csv files. I have to form a star schema using Python. I'm not sure how to create the fact table using Python. The fact table (theoretically) has at least one column that is common with a dimension table. How can I create the fact table, keeping in mind that quantities from multiple dimension tables should correspond correctly in the fact table? I am not allowed to reveal the code or exact data, but I'll add a small example. File 1 contains the

Power BI why circular dependency is detected

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问题 Can you please explain why I run into this alert message of circular dependency when I try to create relationship between dimension #product (or #region) and a #bridge table which is a Cartesian of product x region? I have connected #bridge with Sales and Budget by single column P@G witch is concatenation of product and region. Download file here: PBIX 回答1: A quick and dirty solution is to creat to new versions of #product and #region by using VALUES . This is probably not the best way of

Is there a google supported JDBC driver for BigQuery?

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问题 We are looking to access BigQuery through third party sql clients, ex. RazorSql. I came across StarSchema JDBC driver and I could not make it work with Razorsql and on the webpage it says that the project was archived. So, not sure if its supposed to work. Any suggestions? The error I get when trying to use it with RazoeSql is: java.io.IOException: toDerInputStream rejects tag type 123 I am using a service account key file for authentication. This is JDBC url value I use (where "my-poc" is

Insert into a star-schema

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问题 I've read a lot about star-schema's, about fact/deminsion tables, select statements to quickly report data, however the matter of data entry into a star-schema seems aloof to me. How does one "theoretically" enter data into a star-schema db? while maintaining the fact table. Is a series of INSERT INTO statement within giant stored proc with 20 params my only option (and how to populate the fact table). Many thanks. 回答1: Start with dimensions first -- one by one. Use ECCD (Extract, Clean,

What are the types of dimension tables in star schema design? [closed]

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问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . When reading about star schema design I have seen that many people uses various names for different types of dimension tables. Please

Nulls in dimension table for numeric attributes

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What is the best way to handle missing values in a dimension table? In the case of a textual column, it is easy to write "NA: Missing," but what should be done for numeric columns where it is important to retain the specific values . Note: I do not want a solution that uses banded values (e.g., textual columns for "0-50", "50-100", "NA: Missing"). For instance, a customer dimension may have a year-of-birth. How should missing years of birth be handled? Leave it null? Add in an arbitrary number as a placeholder such as 1900? Sometimes, it may be difficult to find a placeholder number. For

What are the types of dimension tables in star schema design? [closed]

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When reading about star schema design I have seen that many people uses various names for different types of dimension tables. Please list the names and a small description of each type. If any list also an alias name. I have come across these types of dimension tables so far: Regular dimension Standard star dimension. Time Dimension A special case of the standard star dimension. Parent-child dimension Used to model hierarchical structures, fx BOM (bill of materials). Snowflake dimension Can also be used to model hierarchical structures. Degenerate dimensions When the dimension attribute is

Temporary Table Usage in SQL Server

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问题 This is a bit of an open question but I would really like to hear people opinions. I rarely make use of explicitly declared temporary tables (either table variables or regular #tmp tables) as I believe not doing so leads to more concise, readable and debuggable T-SQL. I also think that SQL can do a better job than I of making use of temporary storage when it's required (such as when you use a derived table in a query). The only exception is when the database is not a typical relational

Star vs Snowflake schema in data warehousing?

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问题 Currently, I've been involved in an warehouse based intelligent transaction analysis banking system featuring customer churn behavior, fraud detection & CRM analysis. We've been using Oracle as the database & it's completely a data warehousing project with data mining algorithms used for analysis. We have records of about 1000 customers of a bank. For modeling, whether it is better to use the star schema or snowflake schema or constellation schema? I know the basic difference of star and

Star schema, normalized dimensions, denormalized hierarchy level keys

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Given the following star schema tables. fact, two dimensions, two measures. # geog_abb time_date amount value #1: AL 2013-03-26 55.57 9113.3898 #2: CO 2011-06-28 19.25 9846.6468 #3: MI 2012-05-15 94.87 4762.5398 #4: SC 2013-01-22 29.84 649.7681 #5: ND 2014-12-03 37.05 6419.0224 geography dimension, single hierarchy, 3 levels in hierarchy. # geog_abb geog_name geog_division_name geog_region_name #1: AK Alaska Pacific West #2: AL Alabama East South Central South #3: AR Arkansas West South Central South #4: AZ Arizona Mountain West #5: CA California Pacific West time dimension, two hierarchies, 4