C language and SQL Server database technology

Use ADO.NET Access database

One 、 Use ADO.NET Access database

1.ADO.NET yes   .net framework An important part of

2. yes   .net A technology used by the platform to access databases

3. To operate the database, you first need to connect to the database

4. Connecting to different databases requires different data providers

5. operation SQL  Server The database USES SqlConnection This class , stay System.Date.SqlClient Namespace

6. To connect to the database, you need to provide connection information , These connection information is written in a connection string

                  a、Data  Source  Specify the server where the database is located , It can be localhost perhaps ip Address

                  b、Initial  Catalog  Specify the database to operate

                  c、User  ID  Specify user name

                  d、pwd  Specified password

7. The connection string can be through vs To generate

8. Call the... Of the connection object open（） Method to open the connection

9. Remember to call close（） Method to close the connection , Release resources

10. matters needing attention ：

                 a、 The items in the connection string are separated by English semicolons

                 b、 Server's IP Address 、 Don't write the user name and password wrong

                 c、 Make sure that the database service is started

Two 、 Use ExecuteScalar Query data  

1. You need to execute the query statement , Need to put sql Statements are sent to the database

2.SqlCommand Object is used to sql Statements are sent to the database

3.SqlCommand Object's ExecuteScalar（） Method is used to query the value of the first row and the first column in the result

4. matters needing attention ：

                 a、 Remember to open the database before operation

                 b、ExecuteScalar（） Remember the data type conversion of the returned demerit recording

3、 ... and 、 exception handling

1. The program will inevitably be abnormal

2. After the abnormal , If the program breaks , So the user experience is poor

3. You can usually consider using try  catch Catch exceptions

4.try It contains code that may cause exceptions

5. If there is an anomaly , entering catch（） Intermediate processing