Those who create their sites manually, without the help of designers, or create applications that will interact with the online service, are faced with the problem of data storage. Somewhere it will be necessary to save all user accounts, their data. With what is all this 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, we must learn, MySQL - what it is, what are the features of its application in programming.
Structured Query Language
But you should first find out how queries are made about something. There are a fairly significant number of ways to organize requests for certain data that the information system has. One of these features is a
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 advanced. When using a structured query language, it is necessary to indicate 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. For obtaining insignificant volumes of the necessary data, it fits very well.
Why do I need MySQL?
And where does MySQL come from? What is this all about? As the most discerning readers could understand, 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 usual structured query language is more suitable for working on a computer, while MySQL is more suitable for the web segment.
What is the difference between MySQL and SQL
That is the difference in the segments of the application and lies the main difference. But there are certain procedural differences. So, before working with a database using MySQL queries, you need to get access. 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 constructors called MySQL server).
What are queries?
Now, when the answer is given to the question “MySQL - what is it”, before moving on to possible errors that may arise during the writing of programs, a number of points should be considered: what are queries, databases, tables, and records. And let's start with the queries: they are a short in content encoded message to provide data, and information must be contained on where to look for them, and the keywords by which the search will be carried out. There should be no problems with where to look. But what are keywords? Or how often can you meet the key? To distinguish the necessary data, the principle of unique information is applied. Their quality may be an individual number or other data. But as more advanced, they still use number recognition.
What are databases?
And where is the data that MySQL accesses is stored? Of course, in the 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 created new line. Databases may contain a significant number of tables (conditionally unlimited), but the size of the database affects the speed of response and provision of data. 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 it all depends on the initial conditions - if you work on a paid hosting, everything is almost always installed. But if a server was leased, which should be worked on from scratch, then the MySQL database may not work properly due to the fact that there is no software that will allow you to interpret the data.
What are tables?
Tables, as already mentioned, is a toolkit that stores the necessary data. What is their feature? When creating a table, be sure to indicate to which database it will belong. Situations when tables exist on their own are quite problematic - in view of the fact that 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 in which information is stored for each subject. Everything is simple with the rows - a new subject has appeared - a new row is added (when deleted, it is deleted). Columns are a bit trickier. The fact is that one column can have data of only one type. So, if you work with a numerical column, then you cannot write text to it. And there are quite a few types of different types (about 30, which is already pulling on a separate article).
What are records?
And the last thing before moving on to errors that may occur during the use of MySQL is the record. Each record (or row) must have a unique identifier that allows you to search for it in a table or several tables. There is no potential limitation on its length, but for the convenience of viewing in the "manual" mode, resorting to the reduction in the "normal" form. The essence of this cast is that the record is divided into several parts and placed in different tables. Despite this division, it can be put together thanks to a unique identifier. The meaning of normalization is to group information on objects based on something in common. So, in the library can be created tables "Man", "Books" and "Magazines". Although in practice it would be possible to implement one table with one record, in which all the necessary information will be located.
Possible errors when using
Now you can approach the topic number 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, it is necessary to check its integrity, as well as the request file: it may contain an incorrect database name or password to it. Perhaps the MySQL error message occurs due to the lack of software configuration that should connect to the database and provide information reading.
- 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 the help of debugging tools whether the necessary data arrives at all. If they come, but you cannot use them, it means decoding the received data. In this case, it is advisable to try all the 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 MySQL error can be removed by trying all possible options.