With the foundation of SQLService, you can easily learn about Oracle and sqlserviceoracle.
Recently I want to know about Oracle, and I borrowed some materials from du Niang to learn. Oracle, I know it is also a database, as for other, I do not know. So, let's take a look. Since it is also a database, it should be similar to SQLService. Oracle is currently one of the most popular databases, and many large companies are using it. It has powerful functions and excellent performance. We will undoubtedly design our data before developing the system. Have you carefully considered which database is the best for the system you developed? If you work in a company, we should consider multiple aspects rather than using them at will. We should consider the scale of the project: the size of the load, that is, the size of the user; the cost of the project; the security of the medium-sized system): load: 5000 daily traffic; the cost is within yuan; for example, a business website. Large systems: the load can process massive databases. During testing, many people will find a lot of problems when using them at the same time. Different SQL statements have different execution efficiency, so we must consider which database to choose before development. Large databases are highly secure and expensive. Therefore, we must do what we can. Difference between Oracle and SQLService: their data types are not the same. Oracle only has four data types: ①: numeric, char, varchar2, clob ②: Numeric: number ③: Date: date, timestamp (timestamp) ④: Image: blob, usually does not exist in the data, only for security considerations will be stored in the data. SQLService has many data types, so I won't talk about it. Second, their functions for obtaining the current system time are different: SQLService: getdate (); Oracle: sysdate Oracle how to create a table? For example, to create a student table, some fields are as follows:
create table student(sutdentID number(4),Name varchar2(20),sex char(2),birthday date);
Insert into student valuse ('a001', 'zhang san', 'mal', '01-August-05 ', 10 );
Note: The default date format 'dd-MON-YY 'in Oracle'
If you want to change the date format, you can use the date format we are familiar with, but it is not a permanent modification.
alter session set nls_date_format='yyyy-mm-dd';
Update student set sex = 'male', Name = 'cute dame' where studentID = 'a001 ';
Delete from student; // delete All records. The table structure is still in progress. You can write logs and restore them.
Drop table student; // Delete table structures and Data
Delete from student where studentID = 'a001'; // delete a record
Truncate table student; // delete all the records in the table. The table structure is still in progress and no logs are written. The deleted records cannot be retrieved, but the deletion speed is fast.
In fact, the addition, deletion, modification, and query statements of Oracle are similar to those of SQL Service. Query statements are almost the same. Therefore, with the foundation of SQLService, it is much easier to learn Oracle.
It should be more than just Oracle. I think, there are other things, they should all be the same, with similar similarities. Oracle is worth learning carefully.