#join query

Learn SQL - basic terms Vol II

Next things are JOINs, that allow you to combine tables - to understand how basic JOINs work, imagine two intersecting sets, and all the possibilities of selection of the areas covered by the sets.

JOINs and an example

In your SQL learning process, JOINs will be of utmost importance. So, let’s go through them with an example.

And to understand the work that they do easily, let's start with the INNER JOIN, which operates on two arguments, these are tables in this example, takes them and returns only the records that match a specified beforehand condition in both tables, for instance, there are two tables of children males born in 2000 and second table, of females that were born then, And should you wish to see only the people, regrdless of their sex, who were born in November, that's the job you want the JOINs to give.

So there, a full JOIN, where all the area is selected, left JOIN, where the left set and the common groung, right JOIN, inversely, and inner JOIN that selects only the common ground, where the sets intersect. JOINs if used corerctly ,will get you the results from the tables you need, and the data organization and filtration, also sometmes called in a specific context, normalization, is you can say, the essence of what the data scientists do on their jobs, but in this case, in a nutshell.

That's it, folks, see you in next episode!