这是在VB.net中为连接MySql中编写的一个类库。你可以使用这个类库直接操作MySql数据库。
在使用这个类库之前,你必须安装
ODBC MYSQL 3.51下载地址:http://www.mysql.com/downloads/api-myodbc-3.51.html
Driver ODBC.NET下载地址:http://www.microsoft.com/downloads/details.aspx?FamilyId=6CCD8427-1017-4F33-A062-D165078E32B1&displaylang=en
在这个库中有三个类:
ManipStringForMySQL: 此类修改SGBD的字符串
MySQL_Requettes: 发送请求
MySQL_Utils : 对SGBD数据进行测试
下面是使用此类库操作MySql的一个例子
//对DataSet进行操作
Public Shared Function MyODBCDataset(ByVal ReqSQL As String, _
ByVal LaBase As String, ByVal Server As String, _
ByVal Password As String, ByVal User As String, _
ByVal NomDataSet As String) As DataSet
' Connexion à un server MySQL
'avec le Driver ODBC 3.51 avec requette qui renvoie un dataset
Dim MyConString As String = _
"DRIVER={MySQL ODBC 3.51 Driver};SERVER=" & Server _
& ";DATABASE=" & LaBase & ";UID=" & User _
& ";PASSWORD=" & Password & ";OPTION=3;"
Dim MyODBCConnexion As New OdbcConnection(MyConString)
Try
Dim ds As New DataSet()
Dim cmd As OdbcDataAdapter = New
OdbcDataAdapter(ReqSQL, MyConString)
Dim MyCommand As New OdbcCommand()
Dim MyDataReader As OdbcDataReader
cmd.Fill(ds, NomDataSet)
MyODBCConnexion.Close()
Return ds
Catch MyOdbcException As OdbcException
'
HttpContext.Current.Response.Write(MyOdbcException.ToString)
Catch MyException As Exception
'
HttpContext.Current.Response.Write(MyException.ToString)
End Try
End Function
//对函数的调用
Dim MonDatasetTemp As DataSet = MySQL_Requettes.MyODBCDataset(
SQL,
constantes.ODBCBase,
constantes.ODBCServer,
constantes.ODBCPwd,
constantes.ODBCUser,
"MonDataset")
此程序用到的类库可在如下地址下载:http://www.codeproject.com/dotnet/MySQLConnexion/MySQLConnexion.zip

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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