Therefore, we could easily list all our employees and customers. Our tables are small and have only a few rows. Since we need all pairs in the final report, we’ll need to have 8 report categories (2 employees * 4 customers = 8 different pairs) There are only 3 things worth mentioning here: I guess there is no need to explain SQL queries or their results. These are two tables we’ll need to create all our reporting categories (we need all combinations of employees and customers). We’ll start with the two simple SQL queries to check what is on our tables (employee & customer). We should also return a pair where there were no calls and have 0 as a value in the related column. The goal of this article is to create a report with all pairs of employees and customers and the number of calls each employee and customer had. In this article, we’ll use data from only 3 tables: employee, customer, and call. This will be important when you decide to use INNER JOIN (if you always have a related record) or LEFT JOIN (if you don’t always have a related record) when joining these two tables Which tables are dictionaries and which ones are being populated with data (either by users/customers, either some automated process)? -> You’re interested in analyzing data from tables being populated with the data while dictionaries are here to display info on the screen (when the data is being inserted + used a category in reports)ĭoes table X always have a related record in table Y? -> Maybe there always is a record in the related table, but that doesn’t need to be the case always. Also, you’ll need to be sure how these tables are related. In such a data model, you should identify the tables that contain data needed in the report. Therefore, you can expect that you’ll have a data model at your disposal. If you’re a data analyst, some of the expected tasks you can expect are – grab the data from the database, create a report, draw conclusions from the report data. We’ll start from the simplest possible query and finish with the query returning the actual report data.Īs always, we’ll have to take a look at the data model we’re using. Today we’ll use SQL queries and create a report from scratch. In the previous two articles, we’ve practiced SQL queries and went through a few more examples.

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