Hardware Engineer basic need database, can not use up memory is to use a table. But in the software, if you have not used the database, it is estimated that the interview off relatively hard time, because in the face questions software, database will essentially topic, even if the interview do not ask, in the actual software development, and very hard to find items without a database.
That database is what? Analogy a bit, and our hardware is almost in the table, but the database is a lot of table resting on a file, and then there is the header, table name, database name, the key is to be used sql statement query.
For example, now to be a toy car management system, which would be a database, oracle we have heard of it, their home is the production of large-scale database systems, that we do not have access, too, operate and manage them also inconvenient, our small system with a small database can be, for example, now commonly used in mysql, also free, so now most domestic systems basically use this.
Our toy vehicle management system requires several tables, such as: user table, table vehicle, vehicle operating table, vehicle maintenance table and so on. Then each table represents an entity, known as the software business objects, such as vehicles table bar, where a detour information on the vehicle, such as vehicle number, vehicle type, vehicle aliases, vehicle color, vehicle purchase date and so on, these noun called field, a table how many fields you can set the number of fields.
Some people say, is not that you excel? Yes, inside the excel spreadsheet form called itself a structured file, so it can be seen as a database, of course, mysql database to excel more than the senior, mysql can support multiple threads to read and write, is one of several program can read and write at the same time, this efficiency is much higher.
You may have heard, the operation of the database table has CRUD is to add, delete, modify, query, which can be operated by sql statement, what is the sql statement?
sql statement, as you are a database scripting language, with its own format and compilation engine, for example, a query toy car table, the statement is as follows:
the SELECT * from doll_car_info;
The sentence means that all the information table full of toy cars to check out. Check out what is the result? Software which is called the result set as a result, what is the result set? It is actually a two-dimensional array, transverse rows of vertical columns.
The above mentioned mysql database, we called it a structured relational database, relational what? It is that you can establish a relationship between the tables, and can co-operate.
Since there is a structured relational database, it must also have an unstructured non-relational database, the next section tell you about the unstructured database software project, that is, we often say nosql.
