C language and SQL Server database technology

Use ADO.NET Query and manipulate data

One 、StringBuilder Use

1. The string itself is immutable , String concatenation builds multiple objects , Waste resources

2.StringBuilder It can be directly operated on the string itself , More efficient

3.StringBuilder Object construction ：

                        a、Length    length

                        b、Append（str）    Append string

                        c、AppendFormat（str,params...）    Appending a string with a specific format

                        Insert（index,str）    Insert the specified string in the specified position

                        Remove（startIndex,endIndex）    Delete the string of the specified interval

5. take StringBuilder Convert to string , You can call ToString（） Method

6. If there are not many string operations , You can use it directly String It's more convenient

Two 、 Use ExecutNonQuery Complete the update operation

1.ExecutNonQuery（） Used to perform update operations , Include increase 、 Delete 、 modify

2. The return is int Type the results , Represents the number of rows affected

3. You can judge whether the execution is successful by the number of affected lines

3、 ... and 、DataReader Use

1. Use DataReader You can query the data of the database

2.DataReader Used to retrieve read-only from a data source 、 Only incoming data flow

3.DataReader Only one record can be extracted from the data source at a time

4. operation SQL  Server The database USES SqlDataReader

5.DataReader Common methods ：

                       a、HasRows（）

                       b、Read（） Read down one line , Judge whether there is data , return true or false

                       c、Close（） close

6.DataReader Used up need Close（）

7. adopt SqlCommand Object's ExeuteReader（） Method to get DataReader object

8. Only one cell in one row can be read at a time ：

                       a、 Read according to the subscript of the cell dataReader[0]

                       b、 Read according to the column name of the cell dataReader['stuAge']