From system logon to Data Query

I felt confused when I finished five instances for the first time. Maybe I was just getting started with databases. Many unfamiliar concepts are against the "Eat theory", so I almost lost the motivation for learning.

I have read it for several days, studied it several times, and finally understood it. Today, the meeting concluded, and I learned some new concepts, such as ADO. the main knowledge points and relationships of the five instances are as follows:

Instance 1 System Login

Complete verification by querying the data table that saves the System user login information
Use the entered username to query the password in the data table:

1. Unable to connect to the database, verification cannot be completed
2. The query result is invalid.
3. If the query result is displayed, the user name is correct, and then you can determine whether the entered password is correct.

Instance 2 record view recordset record lock type and temporary table location
Data Source Type
Pointer (EOF and BOF)
Define the process and perform the update operation)
Add multiple records based on instance 1 and switch to display

Instance 3 binds data to the ADO Data Control and connects properties to the data source. The control itself integrates some functions without writing code. Modifications to data can be automatically saved.
It is equivalent to running pre/next in instance 2.
Bind the data source to the text box
Data Environment designer

Instance four-page display record 1. Record set paging attributes:
Copy the records on the current page to the new record set
Display records of the data binding function of the DataGrid Control
2. The msflexgrid control binds data to the Data Control and displays data using the textmatrix attribute.
Added to multi-page display based on instance 3

Instance 5 Data Query ADO command object creation parameter query to query the database
Msflexgrid control display
Database query method:
1. Create a parameter query for the ADO command object to query the database
2. Construct an SQL SELECT statement-An ADO command object or a recordset object to execute a query statement.
3. SELECT statement to obtain database data -- put it into the recordset object -- execute the find method of the recordset object or set the filter attribute to be more comprehensive, including instance 1 input query, and instance 4 Record display

The core of the five instances is database connection. For more information, see the following section.