Those who create their sites manually, without the help of designers, or form an application that will interact with an online service, face the problem of data storage. Somewhere it will be necessary to save all user accounts and their data. With what is it all done? MySQL - what is it, and why is it most relevant to the article? The fact is that this is a mechanism for accessing stored data on various sites or in programs that have access to the network. Therefore, you need to find out MySQL - what it is, what are the features of its use in programming.
Structured Query Language
But first you should find out how requests are made about something. There are quite a significant number of ways to organize queries for certain data that an information system has. One such feature is Structured Query Language (English abbreviation SQL). It allows you to create short queries to select the necessary information. But it can work exclusively with two-dimensional tables, to which a number of requirements are put forward. UsingIn a structured query language, it is imperative to specify the required information and where it should be taken from. You can also set a number of additional requirements, sort them based on some condition, or simply group them. Suitable for small amounts of data required.
Why is MySQL needed?
And what about MySQL? What is it all about? As the most astute readers might have realized, this is a special extension of the Structured Query Language. But where is it used? The fact is that this is a special version for use in the web programming segment. The regular structured query language is more designed to work on a computer, while MySQL is more for the web segment.
What is the difference between MySQL and SQL
The main difference lies in the difference between application segments. But there are also certain procedural differences. So, before working with a database using MySQL queries, you need to gain access. Yes, and the work of MySQL itself is, to put it mildly, impossible. Therefore, another additional programming language is often used (most often PHP, although you can also find connection creation constructors called MySQL server).
What are requests?
Now that the answer to the question "MySQL - what is it" is given, before moving on to possible errors that may occur while writing programs, a number of points should be considered: what are queries, databases, tables and records. Andlet's start with requests: they are a short coded message for the provision of data, and must contain information about where to look for them, and the keywords by which the search will be carried out. Where to look should not be a problem. But what are keywords? Or how often can a key be encountered? To distinguish the required data, the principle of unique information is used. They can be an individual number or other data. But as more advanced, license plate recognizers are still used.
What are databases?
Where is the data that is accessed through MySQL stored? Of course, in databases! In MySQL, they are two-dimensional tables that contain the necessary information. Moreover, they are identified by the value of the data that can be in the database thanks to the columns. And information about each new subject is added to the new line being created. Databases can contain a significant number of tables (conditionally unlimited), but the size of the database affects the speed of response and data provision. But before working with the database, you need to make sure that there is support for the necessary software and MySQL Server can start. Although everything here depends on the initial conditions - if you work on paid hosting, everything is almost always installed. But if a server was rented that should be worked on from scratch, then the MySQL database may not work properly due to the fact that there is no softwaresoftware to interpret the data.
What are tables?
Tables, as already mentioned, are tools that store the necessary data. What is their feature? When creating a table, be sure to specify which database it will belong to. Situations where tables exist on their own are quite problematic, since most software tools are designed to interact with certain programs.
What do MySQL tables usually look like? They have columns of information (of a certain type of data) and rows that store information for each subject. With rows, everything is simple - a new subject has appeared - a new row is added (when deleted, it is deleted). Columns are a bit trickier. The matter is that one column can have the data of only one type. So, if you work with a numeric column, then you cannot write text to it. And there are quite a few types of different types (about 30, which is already a separate article).
What are records?
And the last thing before moving on to the errors that can occur when using MySQL - records. Each record (or row) must have a unique identifier that allows it to be searched for in a table or multiple tables. Potentially, there is no limit on its length, but for the convenience of viewing in the "manual" mode, they resort to bringing it into "normal" forms. The essence of such a reduction is that the recordis divided into several parts and placed in different tables. Despite this division, it can be put together thanks to a unique identifier. The point of normalization is to group information into objects based on something in common. So, tables "Person", "Books" and "Journals" can be created in the library. Although in practice it would be possible to implement one table with one record, which will contain all the necessary information.
Possible errors when using
Now we can come to topic 2. What causes errors? In most cases, the human factor is to blame. This may be an elementary error that crept into the code during its typing, or an incorrectly composed request:
- If there is an error connecting to the database, you need to check its integrity, as well as the request file: it may contain an incorrect database name or password. It is possible that the MySQL error message is due to a lack of configuration of the tool that should connect to the database and read the information.
- When requesting data from tables, you need to take care of high-quality decryption of information, as well as the reverse transfer of information from the MySQL server to you. As mentioned above, as a rule, MySQL is used with the support of "intermediaries", so it will not be superfluous to check with debugging tools whether the necessary data is coming at all. If they come, but you cannot use them, it means that the matter is in decoding the received data. ATIn this case, it is advisable to try all working options, starting with the smallest working volumes. It should be remembered, especially for those who are just starting to comprehend programming, that this is such an area where everything is decided by practice, and you can remove the MySQL error yourself by trying all possible options.
