Those who create their sites manually, without the help of designers, or form applications that interact with the online service, face the problem of data storage. Somewhere, it will be necessary to save all user accounts, their data. With the help of what is this all carried out? MySQL - what is it, and why is it most relevant to the article? The point is that this is a mechanism for accessing stored data on various sites or in programs that have access to the network. That's why you need to know, MySQL - what it is, what are the features of its application in programming.
Structured Query Language
But first you should find out how queries are made about something at all. There are quite a number of ways to organize requests for certain data that the information system has. One of these features is the structured query language (English abbreviation of SQL). It allows you to create short queries for the selection of necessary information. But he can work exclusively with two-dimensional tables, which are put forward a number of requirements. When using structured query language, it is necessary to indicate the required information and where it should be taken. You can also specify a number of additional requirements, sort, based on some condition, or simply group. To obtain insignificant amounts of necessary data, it is very suitable.
Why MySQL?
And where does MySQL come in? What is this? As the most ingenious 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 segment of web programming. The common language of structured queries is more designed to work on the computer, while MySQL is designed for the Web segment.
What is the difference between MySQL and SQL?
Here's the difference in the application segments and is the main difference. But there are certain procedural differences. So, before you can work with the database using MySQL queries, you need to 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 meet the connection creation constructors, which call the MySQL server).
What are queries?
Now, when the answer to the question "MySQL - what it is" is, before proceeding to possible errors that may occur during the writing of programs, you should consider a number of other points: what are queries, databases, tables and records. And let's start with the queries: they are a brief encoded message for the provision of data, which must contain information about where to find them and the keywords for which the search will be carried out. With where to look, there should not be any problems. But what are keywords? Or how often can I find a key? To distinguish the necessary data, the principle of unique information is applied. In their capacity, an individual number or other data may act. But as more advanced, however, numbered recognizers are used.
What are databases?
And where are the data stored to which MySQL accesses? Of course, in databases! In MySQL, they are two-dimensional tables that contain the necessary information. And are identified by the value of the data that can be in the database due to the columns. And information about each new subject is added to the new line being created. The 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 will be able to start. Although everything here depends on the initial conditions - if you work on paid hosting, everything is almost always installed. But if you have leased a server that you need to work on from scratch, the MySQL database might not work properly because 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, you must specify which database it belongs to. Situations when tables exist by themselves are rather problematic - in view of the fact that most software tools are designed to interact with certain programs.
What do MySQL tables look like? They have columns of information (a certain type of data) and rows in which information is stored for each subject. With the rows everything is simple - a new subject has appeared - a new series is added (when deleted, it is deleted). The columns are slightly more complicated. The fact is that one column can have data of only one type. So, if you work with a numeric column, you can not write the text in it. And there are quite a few types of types (about 30, which already draws on a separate article).
What are entries?
And the very last before going to the errors that can arise in the process of using MySQL, are records. Each record (or row) must have a unique identifier that will allow it to be searched in a table or several tables. Potentially, there is no limit to its length, but for convenience of viewing in "manual" mode resort to bringing in "normal" forms. The essence of this reduction is that the record is divided into several parts and placed in different tables. Despite such a division, it can be put together by a unique identifier. The meaning of bringing to normal forms is to group information on objects on the basis of something common. Thus, in the library, tables "Man", "Books" and "Journals" can be created. Although in practice it would be possible to implement one table with one record, which will contain all the necessary information.
Possible errors in use
Now you can go to the topic number 2. What causes errors? In most cases, the human factor is at fault. This can be an elementary error that has crept into the code during its set, or an incorrectly composed query:
- If there is an error connecting to the database, you need to check its integrity, as well as the request file: it may indicate an incorrect database name or password to it. Perhaps the MySQL error message occurs because there is no configuration of the software that must connect to the database and ensure that the information is read.
- When requesting data from the tables, you need to take care of the qualitative decryption of information, as well as the return 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 using debugging tools to see if the necessary data comes at all. If they come, but you can not use them - it means the case in decoding the received data. In this case, it is desirable to try all working options, starting with the lowest working volumes. It should be remembered, especially for those who are just beginning to comprehend programming, that this is an area where everything is decided by practice, and MySQL error can be removed by itself, having tried all possible variants.