Figure: Inner Join. Image source:DataCamp SQL-Join cheat sheet. SELECTo.order_id,c.nameFROMorders oINNERJOINcustomers cONo.customer_id=c.customer_id; Anouter joinreturns all rows from one table and the matching rows from the other. If there is no match, NULL values are returned for column...
Conversion Functions are used to convert one data type into another. Convert functions differ from server to server. Here I will give you an example of an Oracle server query that uses the to_char function. This will help you understand how you can use conversion functions to customize the ...
what you want is to group all the males together and count them, and group all the females together and count them. In SQL, GROUP BY allows you to group a result by one or more columns, like so:datacamp group by
This is a 4-course beginner level program and is an excellent fit for those who want to learn to query big data with modern distributed SQL engines, whether or not they have any experience in SQL. The SQL SELECT statement and its main clauses are discussed in detail in one of the cours...
One of SQL’s most powerful features is its ability to connect different tables of information. Think of it as solving a puzzle – each table is a piece, and when you connect them correctly, a complete picture emerges. According to DataCamp’s recent study, understanding how to connect tabl...
最近在DataCamp上学习SQL(基于PostgreSQL)的课程,本文主要记录自己易记混的点,以便日后参考学习,不做原理讲解。 GROUP BY(分组)一般和聚合函数一起使用,包括COUNT(),AVG(),MAX(),MIN(),SUM();一般跟在FROM后面;SELECT语句中未出现在聚合函数里的列都要出现在GROUP BY。
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DataCamp’sDatabase Designcourse teaches the foundations of efficient database design. It covers considerations related to the processing, storage, and organization of data. The main focus in this course is SQL; you’ll learn how to structure data with normalization and summarize data from different...
We learned a lot about user behaviour, trends, and how we reached (or didn’t reach) our goals. I loved it – except for one thing: I always had to wait days (sometimes weeks) for the developers to export the data for me from the company’s SQL database. ...