Option Explicit
'==================================== 声明属性 =================================Private Con As ADODB.Connection
' ====================================声明事件===================================
'==================================== 初始化 类 ===================================
Private Sub Class_Initialize()
Set Con = New ADODB.Connection
Con.CursorLocation = adUseClient '设置此项才可获取 recordset.RecordCount
Con.ConnectionString = "Driver={MySQL ODBC 5.2 ANSI Driver};" + _
"Server=sc;" + _
"DB=oa;" + _
"UID=UID;" + _
"PWD=PWD;" + _
"OPTION=3;" + _
"Stmt=Set Names 'UTF-8';"
End Sub
'=================================== 以“属性”的形式对 私有变量 读取、赋值 ====================================
'=================================== 公有方法 ====================================
'关闭连接
Public Sub closeConnection()
Con.Close
Set Con = Nothing
End Sub
'检测是否连接成功
Public Sub checkConnection()
Con.Open
If Con.State = adStateOpen Then
MsgBox "链接状态:" & Con.State & vbCrLf & "ADO版本:" & Con.Version, vbInformation, ""
End If
closeConnection '关闭连接
End Sub
'将查询得到的记录显示到指定 单元格
Public Sub recordToCell(sqlStr As String, wBook, wSheet, firstCell As String)
Dim thisRec As ADODB.Recordset
'查询记录
Set thisRec = selectRecord(sqlStr)
'写入到指定 单元格
Workbooks(wBook).Sheets(wSheet).Range(firstCell).CopyFromRecordset thisRec
closeConnection '关闭连接
End Sub
'============= 数据库 “插、查、改、删” ==============
'“删除”用“更改”[标记删除]实现)
'①“插入”一条记录(返回值:1成功,-1已有相同值,0失败)
'db 数据库名
'fieldArray 字段名 数组
'valueArray 字段值 数组
'checkField 用于检查是否已有相同记录的 字段名(field1,field2,……)
Public Function inertRecord(db As String, fieldArray, valueArray, checkField As String) As Integer
'检查是否已有相应记录
Dim insertRow As Integer
Dim rec As ADODB.Recordset
Dim checkFV, fieldValue, insertSql As String
' MsgBox TypeName(fieldArray)
checkFV = Join(fieldAndValue(fieldArray, valueArray, checkField), " AND ")
fieldValue = Join(fieldAndValue(fieldArray, valueArray), ",")
Set rec = selectRecord(db, "id", checkFV)
If rec.RecordCount
insertSql = "INSERT INTO `" & db & "` SET " & fieldValue
Con.Execute insertSql, insertRow, adCmdText
inertRecord = IIf(insertRow = 1, 1, 0)
Else
inertRecord = -1
End If
Set rec = Nothing
End Function
'②按条件“查询”记录(返回值:ADODB.Recordset对象)
'db 数据库名
'fields 要查询的字段名(field1,field2,……)
'where 查询条件(`field1`='value1' AND|OR `field2`='value2' AND|OR ……)
'sortFields 排序工序(field1,field2[DESC],……)
'limit 要查询的记录数(100 或 20,100)
Public Function selectRecord(db As String, Optional fields = "*", _
Optional where = "", Optional sortFields = "", Optional limit = "") As ADODB.Recordset
Dim sqlStr As String
sqlStr = "SELECT " & fields & " FROM `" & db & "`"
If where "" Then sqlStr = sqlStr & " WHERE " & where
If sortFields "" Then sqlStr = sqlStr & " ORDER BY '" & sortFields & "'"
If limit "" Then sqlStr = sqlStr & " LIMIT " & limit
' MsgBox sqlStr
Set selectRecord = allSql(sqlStr) '总查询 (执行sql语句方法)
End Function
'③“更改”符合指定条件的记录的指定字段(返回受影响的行数)
'db 数据库名
'fieldArray 字段名 数组
'valueArray 字段值 数组
'where 条件(`field1`='value1' AND|OR `field2`='value2' AND|OR ……)
Public Function updateRecord(db As String, fieldArray, valueArray, where As String) As Integer
Dim updateRows As Integer
Dim updateSql, fieldValue As String
fieldValue = Join(fieldAndValue(fieldArray, valueArray), ",")
If fieldValue "" Then
updateSql = "UPDATE `" & db & "` SET " & fieldValue & " WHERE " & where
Con.Open
Con.Execute updateSql, updateRows, adCmdText
updateRecord = IIf(updateRows 0, updateRows, 0)
End If
End Function
'总查询 (执行sql语句方法)
Public Function allSql(sqlStr) As ADODB.Recordset
Dim iRowscount As Long
Con.Open
Set allSql = Con.Execute(sqlStr, iRowscount, adCmdText)
End Function
'=================================== 私有方法 ====================================
'将 fieldArray、valueArray 连接成 `field`='value'(Array)并返回 “数组”
'(若 onlyField 不为空,则只连接包含其内元素的 field)
Private Function fieldAndValue(fieldArray, valueArray, Optional onlyField = "")
Dim i, s As Integer
Dim fj_onlyField(), fvArray()
' MsgBox fieldArray(0)
For i = 0 To UBound(fieldArray)
If fieldArray(i) "" Then
If onlyField = "" Then
ReDim Preserve fvArray(i)
fvArray(i) = "`" & fieldArray(i) & "`='" & valueArray(i) & "'"
Else
If InStr(onlyField, ",") > 0 Then
fj_onlyField = Split(onlyField, ",")
If checkArrayValue(fj_onlyField, fieldArray(i)) = True Then
ReDim Preserve fvArray(s)
fvArray(s) = "`" & fieldArray(i) & "`='" & valueArray(i) & "'"
s = s + 1
End If
Else
If onlyField = fieldArray(i) Then
ReDim Preserve fvArray(0)
fvArray(0) = "`" & fieldArray(i) & "`='" & valueArray(i) & "'"
Exit For
End If
End If
End If
End If
Next i
fieldAndValue = fvArray
End Function
'检测数组中是否包含有=指定值的元素
Private Function checkArrayValue(arr, theValue) As Boolean
Dim i As Integer
checkArrayValue = False
For i = 0 To UBound(arr)
If arr(i) = theValue Then
checkArrayValue = True
Exit For
End If
Next i
End Function
'将 html实体 转换成正常字符(可用)
Private Function htmlDecodes(str As String) As String
If str = "" Then
htmlDecodes = ""
Else
str = Replace(str, "<", "<")
str = Replace(str, ">", ">")
str = Replace(str, "&", "&")
str = Replace(str, """, Chr(34))
str = Replace(str, ">", Chr(39))
htmlDecodes = str
End If
End Function

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.

SQL commands in MySQL can be divided into categories such as DDL, DML, DQL, DCL, etc., and are used to create, modify, delete databases and tables, insert, update, delete data, and perform complex query operations. 1. Basic usage includes CREATETABLE creation table, INSERTINTO insert data, and SELECT query data. 2. Advanced usage involves JOIN for table joins, subqueries and GROUPBY for data aggregation. 3. Common errors such as syntax errors, data type mismatch and permission problems can be debugged through syntax checking, data type conversion and permission management. 4. Performance optimization suggestions include using indexes, avoiding full table scanning, optimizing JOIN operations and using transactions to ensure data consistency.

InnoDB achieves atomicity through undolog, consistency and isolation through locking mechanism and MVCC, and persistence through redolog. 1) Atomicity: Use undolog to record the original data to ensure that the transaction can be rolled back. 2) Consistency: Ensure the data consistency through row-level locking and MVCC. 3) Isolation: Supports multiple isolation levels, and REPEATABLEREAD is used by default. 4) Persistence: Use redolog to record modifications to ensure that data is saved for a long time.

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL is suitable for small and large enterprises. 1) Small businesses can use MySQL for basic data management, such as storing customer information. 2) Large enterprises can use MySQL to process massive data and complex business logic to optimize query performance and transaction processing.

InnoDB effectively prevents phantom reading through Next-KeyLocking mechanism. 1) Next-KeyLocking combines row lock and gap lock to lock records and their gaps to prevent new records from being inserted. 2) In practical applications, by optimizing query and adjusting isolation levels, lock competition can be reduced and concurrency performance can be improved.


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DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software