场景
Sqlite数据库
SQLite是一个进程内的库，实现了自给自足的、无服务器的、零配置的、事务性的 SQL 数据库引擎。
它是一个零配置的数据库，这意味着与其他数据库不一样，您不需要在系统中配置。
就像其他数据库，SQLite 引擎不是一个独立的进程，可以按应用程序需求进行静态或动态连接。
SQLite 直接访问其存储文件。
需求是在Winform程序启动时进行本地建库建表，然后进行增删改查的逻辑操作。
注：
博客：
霸道流氓气质的博客_CSDN博客-C#,架构之路,SpringBoot领域博主
实现
1、本文直接参考博客
SQLite操作指南之.NET篇
https://www.cnblogs.com/wml-it/p/16574254.html
进行调用和适配。
2、Nuget安装System.Data.SQLite.Core
3、封装操作Sqlite的帮助类SqLiteHelper
class SqLiteHelper
{
/// <summary>
/// 数据库连接定义
/// </summary>
private SQLiteConnection dbConnection;
/// <summary>
/// SQL命令定义
/// </summary>
private SQLiteCommand dbCommand;
/// <summary>
/// 数据读取定义
/// </summary>
private SQLiteDataReader dataReader;
/// <summary>
/// 构造函数
/// </summary>
/// <param name="connectionString">连接SQLite库字符串</param>
public SqLiteHelper(string connectionString)
{
try
{
dbConnection = new SQLiteConnection(connectionString);
dbConnection.Open();
}
catch (Exception e)
{
Log(e.ToString());
}
}
/// <summary>
/// 执行SQL命令
/// </summary>
/// <returns>The query.</returns>
/// <param name="queryString">SQL命令字符串</param>
public SQLiteDataReader ExecuteQuery(string queryString)
{
try
{
dbCommand = dbConnection.CreateCommand();
dbCommand.CommandText = queryString;
dataReader = dbCommand.ExecuteReader();
}
catch (Exception e)
{
Log(e.Message);
}
return dataReader;
}
/// <summary>
/// 关闭数据库连接
/// </summary>
public void CloseConnection()
{
//销毁Commend
if (dbCommand != null)
{
dbCommand.Cancel();
}
dbCommand = null;
//销毁Reader
if (dataReader != null)
{
dataReader.Close();
}
dataReader = null;
//销毁Connection
if (dbConnection != null)
{
dbConnection.Close();
}
dbConnection = null;
}
/// <summary>
/// 读取整张数据表
/// </summary>
/// <returns>The full table.</returns>
/// <param name="tableName">数据表名称</param>
public SQLiteDataReader ReadFullTable(string tableName)
{
string queryString = "SELECT * FROM " + tableName;
return ExecuteQuery(queryString);
}
/// <summary>
/// 向指定数据表中插入数据
/// </summary>
/// <returns>The values.</returns>
/// <param name="tableName">数据表名称</param>
/// <param name="values">插入的数值</param>
public SQLiteDataReader InsertValues(string tableName, string[] values)
{
//获取数据表中字段数目
int fieldCount = ReadFullTable(tableName).FieldCount;
//当插入的数据长度不等于字段数目时引发异常
if (values.Length != fieldCount)
{
throw new SQLiteException("values.Length!=fieldCount");
}
string queryString = "INSERT INTO " + tableName + " VALUES (" + "'" + values[0] + "'";
for (int i = 1; i < values.Length; i++)
{
queryString += ", " + "'" + values[i] + "'";
}
queryString += " )";
return ExecuteQuery(queryString);
}
/// <summary>
/// 更新指定数据表内的数据
/// </summary>
/// <returns>The values.</returns>
/// <param name="tableName">数据表名称</param>
/// <param name="colNames">字段名</param>
/// <param name="colValues">字段名对应的数据</param>
/// <param name="key">关键字</param>
///<paramname="value">关键字对应的值</param><BR> ///<paramname="operation">运算符：=,<,>,...，默认“=”</param>
public SQLiteDataReader UpdateValues(string tableName, string[] colNames, string[] colValues, string key, string value, string operation = "=")
{
//当字段名称和字段数值不对应时引发异常
if (colNames.Length != colValues.Length)
{
throw new SQLiteException("colNames.Length!=colValues.Length");
}
string queryString = "UPDATE " + tableName + " SET " + colNames[0] + "=" + "'" + colValues[0] + "'";
for (int i = 1; i < colValues.Length; i++)
{
queryString += ", " + colNames[i] + "=" + "'" + colValues[i] + "'";
}
queryString += " WHERE " + key + operation + "'" + value + "'";
return ExecuteQuery(queryString);
}
/// <summary>
/// 删除指定数据表内的数据
/// </summary>
/// <returns>The values.</returns>
/// <param name="tableName">数据表名称</param>
/// <param name="colNames">字段名</param>
/// <param name="colValues">字段名对应的数据</param>
public SQLiteDataReader DeleteValuesOR(string tableName, string[] colNames, string[] colValues, string[] operations)
{
//当字段名称和字段数值不对应时引发异常
if (colNames.Length != colValues.Length || operations.Length != colNames.Length || operations.Length != colValues.Length)
{
throw new SQLiteException("colNames.Length!=colValues.Length || operations.Length!=colNames.Length || operations.Length!=colValues.Length");
}
string queryString = "DELETE FROM " + tableName + " WHERE " + colNames[0] + operations[0] + "'" + colValues[0] + "'";
for (int i = 1; i < colValues.Length; i++)
{
queryString += "OR " + colNames[i] + operations[0] + "'" + colValues[i] + "'";
}
return ExecuteQuery(queryString);
}
/// <summary>
/// 删除指定数据表内的数据
/// </summary>
/// <returns>The values.</returns>
/// <param name="tableName">数据表名称</param>
/// <param name="colNames">字段名</param>
/// <param name="colValues">字段名对应的数据</param>
public SQLiteDataReader DeleteValuesAND(string tableName, string[] colNames, string[] colValues, string[] operations)
{
//当字段名称和字段数值不对应时引发异常
if (colNames.Length != colValues.Length || operations.Length != colNames.Length || operations.Length != colValues.Length)
{
throw new SQLiteException("colNames.Length!=colValues.Length || operations.Length!=colNames.Length || operations.Length!=colValues.Length");
}
string queryString = "DELETE FROM " + tableName + " WHERE " + colNames[0] + operations[0] + "'" + colValues[0] + "'";
for (int i = 1; i < colValues.Length; i++)
{
queryString += " AND " + colNames[i] + operations[i] + "'" + colValues[i] + "'";
}
return ExecuteQuery(queryString);
}
/// <summary>
/// 创建数据表
/// </summary> +
/// <returns>The table.</returns>
/// <param name="tableName">数据表名</param>
/// <param name="colNames">字段名</param>
/// <param name="colTypes">字段名类型</param>
public SQLiteDataReader CreateTable(string tableName, string[] colNames, string[] colTypes)
{
string queryString = "CREATE TABLE IF NOT EXISTS " + tableName + "( " + colNames[0] + " " + colTypes[0];
for (int i = 1; i < colNames.Length; i++)
{
queryString += ", " + colNames[i] + " " + colTypes[i];
}
queryString += " ) ";
return ExecuteQuery(queryString);
}
/// <summary>
/// Reads the table.
/// </summary>
/// <returns>The table.</returns>
/// <param name="tableName">Table name.</param>
/// <param name="items">Items.</param>
/// <param name="colNames">Col names.</param>
/// <param name="operations">Operations.</param>
/// <param name="colValues">Col values.</param>
public SQLiteDataReader ReadTable(string tableName, string[] items, string[] colNames, string[] operations, string[] colValues)
{
string queryString = "SELECT " + items[0];
for (int i = 1; i < items.Length; i++)
{
queryString += ", " + items[i];
}
queryString += " FROM " + tableName + " WHERE " + colNames[0] + " " + operations[0] + " " + colValues[0];
for (int i = 0; i < colNames.Length; i++)
{
queryString += " AND " + colNames[i] + " " + operations[i] + " " + colValues[0] + " ";
}
return ExecuteQuery(queryString);
}
/// <summary>
/// 本类log
/// </summary>
/// <param name="s"></param>
static void Log(string s)
{
Console.WriteLine("class SqLiteHelper:::" + s);
}
}注意这里的引入
using System;
using System.Data.SQLite;4、如果需要在程序启动时执行建库建表等操作，只需要在Program.cs中添加执行代码
上面参考博客中的使用示例
class Program
{
private static SqLiteHelper sql;
static void Main(string[] args)
{
sql = new SqLiteHelper("data source=StudentSystem.db");
//创建名为table1的数据表
sql.CreateTable("Students", new string[] { "ID", "Name", "Age", "Email" }, new string[] { "INTEGER", "TEXT", "INTEGER", "TEXT" });
//插入两条数据
sql.InsertValues("Students", new string[] { "1", "张三", "22", "Zhang@163.com" });
sql.InsertValues("Students", new string[] { "2", "李四", "25", "Li4@163.com" });
//更新数据，将Name="张三"的记录中的Name改为"Zhang3"
sql.UpdateValues("Students", new string[] { "Name" }, new string[] { "ZhangSan" }, "Name", "Zhang3");
//删除Name="张三"且Age=26的记录,DeleteValuesOR方法类似
sql.DeleteValuesAND("Students", new string[] { "Name", "Age" }, new string[] { "张三", "22" }, new string[] { "=", "=" });
//读取整张表
SQLiteDataReader reader = sql.ReadFullTable("Students");
while (reader.Read())
{
//读取ID
Log("ID:" + reader.GetInt32(reader.GetOrdinal("ID")));
//读取Name
Log("NAME:" + reader.GetString(reader.GetOrdinal("Name")));
//读取Age
Log("Age:" + reader.GetInt32(reader.GetOrdinal("Age")));
//读取Email
Log("Email:" + reader.GetString(reader.GetOrdinal("Email")));
}
Console.ReadLine();
}
static void Log(string s)
{
Console.WriteLine(s);
}
}这里只需要在启动后执行建库建表的操作，所以在Program.cs中执行封装的全局工具类方法
namespace DataConvert
{
static class Program
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
//顺序勿动
//初始化positions数据库
Global.Instance.InitPositionSqLite();
Application.Run(new Form1());
}
}
}如上添加一行
Global.Instance.InitPositionSqLite();注意这行添加的位置。
然后构建一个单例的全局工具类Global
class Global
{
private SqLiteHelper _sqlLiteHelper;
private static string _lockFlag = "GlobalLock";
private static Global _instance;
//mqtt是否已经连接
public bool isMqttClientConnected = false;
private Global()
{
}
public static Global Instance
{
get
{
lock (_lockFlag)
{
if (_instance == null)
{
_instance = new Global();
}
return _instance;
}
}
}
public SqLiteHelper sqlLiteHelper
{
get { return _sqlLiteHelper; }
set { _sqlLiteHelper = value; }
}
public void InitPositionSqLite()
{
_sqlLiteHelper = new SqLiteHelper("data source=positions.db");
//创建名为positions的数据表
_sqlLiteHelper.CreateTable("positions", new string[] { "timestamp", "data" }, new string[] { "TEXT", "TEXT" });
}
}添加一个方法，用来实例化SqlLiteHelp的实例执行建库建表操作
这里创建名为positions.db的库，并且创建名为positions的表，然后该表有两个字段timestamp和data，全部为字符串文本格式。
5、项目启动后查看exe所在同目录下的db文件已经创建成功
6、Sqlite可视化工具DB Browser for SQLite的下载与使用
DB Browser for SQLite:
mirrors / sqlitebrowser / sqlitebrowser · GitCode
下载地址:
Downloads – DB Browser for SQLite
下载并在Windows上解压打开后，双击
DB Browser for SQLite.exe
启动，然后打开数据库，选择上面的db文件
这里可以看到表以及浏览数据和执行sql等操作
7、这样的话就可以在Form1.cs等页面中执行增删改查的逻辑
插入数据时就可以
Global.Instance.sqlLiteHelper.InsertValues("positions", new string[] { time2, "霸道的程序猿"});其中time2是获取的当前时间戳字符串。
读取整张表的数据
SQLiteDataReader reader = Global.Instance.sqlLiteHelper.ReadFullTable("positions");
while (reader.Read())
{
//读取
Console.WriteLine("timestamp:" + reader.GetString(reader.GetOrdinal("timestamp")));
Console.WriteLine("data:" + reader.GetString(reader.GetOrdinal("data")));
}如果要读取Sqlite指定表中的前多少行，可以通过执行Sqlite的自定义语句的方式实现
比如要查询前6行
SQLiteDataReader reader = Global.Instance.sqlLiteHelper.ExecuteQuery("SELECT* FROM positions LIMIT 6;");其他操作都可以通过执行sql语句的方式执行，比如删除指定条件的数据
Global.Instance.sqlLiteHelper.ExecuteQuery("DELETE FROM positions WHERE timestamp = "+ reader.GetString(reader.GetOrdinal("timestamp"))+";");这里是查询出前6行并挨个操作后删除。
其他更多Sqlite语句的写法和示例可自行网上搜索
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