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This article mainly explains "what are the problems encountered in learning SQL". The content of the explanation in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn what are the problems in learning SQL.

Database installation and uninstall error

I have a detailed description of each step of these two problems on the official account, including the preparation conditions before installation, the points needing attention in the installation process, and how to solve errors reported during the installation process.

I will not repeat it here. Friends who need it can go to the official account to search for historical articles.

And some are more piecemeal and not easy to tweet. So how did I solve it?

SQL code reported an error

For such problems, the general system will give hints, such as the following

Yes, I can see the problem, so I just point it out. Some can't see it, so they have to seek Baidu. Enter the error message directly, nine times out of ten, there will be a solution to a similar problem, and sometimes you don't even need to enter the full error message, just enter the error code.

But there are so many solutions, which one is right? It depends on how well the solution fits your mistake. If it is completely consistent, it can not be said to be it. If there are individual differences, you can look at a few more solutions and then choose to use them.

In addition, the error code is also divided into platforms, so when searching, I will add the name of the database platform, such as the error code of Mysql, and I will add a Mysql before the error code, so that I will not find the same error code in Oracle or SQL Server.

Technical problems of SQL

These are generally questions about how to achieve it, such as how to solve the time difference between the upper and lower adjacent lines, how to write the contents of the same group to one line, how to count the flow of people every 5 minutes, and so on.

All of the above problems can be summed up as logic problems. Although SQL is not omnipotent, it is its strength in dealing with logic problems.

For example, the time difference between two adjacent lines can be offset and subtracted by adding self-growing ID. Or you can use functions provided by the system, such as SQL Server and Oracle, which have functions for Lead () and Lag () to shift N rows forward and backward (the default is offset by 1 row), and then subtract from the original column.

This kind of problem really needs experience to solve. I don't like to give them complete code directly when answering such questions. More often, I will tell them what to do and what technical points to use.

Because you give them the code directly, you may not think about it and will not take the time to understand the role of these technical points. Over time, I still haven't learned some more practical skills.

Thank you for your reading, the above is the content of "what are the problems encountered in learning SQL". After the study of this article, I believe you have a deeper understanding of what problems you encounter in learning SQL, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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