Database query language (1)

Author: scholar
Starting from this article, we will introduce ASP built-in ActiveX.
Components, but considering that we will be exposed to a large number of database queries in the future, therefore, the author temporarily decided to spend one or two articles to brief you on the basic knowledge of some database query languages.
ASP
A required knowledge. Whether the database query language can be used flexibly is directly related
ASP program execution efficiency and other issues, so please pay attention to it.
I believe many of my friends have heard of SQL
This name, if you are a computer expert, SQL
The name must be like this. So what is SQL? The word SQL is actually
"Structured Query Language"
The abbreviation of structured query language is used to organize, manage, and retrieve data stored in computer databases. It is a specific type of database.
-- Relational database. Computer programs that control such databases are what we often say.
DBMS-database management system. For example: SQL Server, Oracle, Sybase, DB2
And so on. When a user wants to retrieve data in a database
Then, the DBMS sends a request to the SQL
Request processing and retrieval of the required data, and finally return it to the user, this process is called as a database query, this is the origin of the database query language name.
SQL is not a complete computer language like C, COBOL, or Fortran. SQL
There is no IF statement for conditional testing, and no Goto statement for program Branch
Statement and loop statement For or Do. Specifically, SQL is a database sub-language.
Statements can be embedded in another language to enable database access. SQL
It is not a strictly structured language, and its syntax is closer to the English statement, so it is easy to understand.
The SQL statement is just like a natural language. SQL
It is also an interactive query language that allows users to directly query stored data. With this interactive feature, users can answer quite complex questions in a short period of time, however, it may take weeks or even longer for programmers to write corresponding report programs.
In most ASP applications, we have access to the database, and we are writing
The standard syntax used for database operations in ASP applications is SQL.
The importance of syntax is self-evident. Next, we will start from the most commonly used SQL statement SELECT
Start by Learning SQL step by step.
Query is the core of SQL, and is used to express the SELECT statement of SQL query.
Statements are the most functional and complex SQL statements.
Statement, which retrieves data from the database and provides the query results to the user. In this article, we will create