SQLite 之 C#版 System.Data.SQLite 使用

简介

SQLite简介

    SQLite，是一款轻型的关系型数据库。它的设计目标是嵌入式。

    它能够支持Windows/Linux/Unix等等主流的操作系统，同时能够跟很多程序语言相结合，比如 C++、C#、Object-C、PHP、Java等。

    我是做手游开发的，在手机上使用SQLite 存储数据是很方便的。 

System.Data.SqLite实践前期准备

1. System.Data.SQLite 库下载，用于C#操作SQLite的dll文件。下载地址：http://system.data.sqlite.org/index.html/doc/trunk/www/downloads.wiki
2. SQLite可视化工具下载，用于查看SQLite库数据表数据。下载地址：http://www.sqliteexpert.com/download.html

Tips:

    1.根据自己的电脑是64bit或者32bit 以及使用的.NET Freamwork版本下载相应的的System.Data.SQLite。    下载解压文件如：

     安装在指定目录后生成多个dll文件：

     本文测试用的只有 System.Data.SQLite.dll 。对于SQLite库数据的增删改查已经足够用了。

    2.SQLite数据库文件以.db为后缀。安装SQLite可视化工具后如图：

     mydb是我测试用的数据库。

实践

    对SQLite的增、删、改、查。

    测试环境：VS2015  语言：C#

    创建控制台新工程，引入System.Data.SQLite.dll 文件。   

    1.编写SQLite 操作类， 对SQLite数据操作进行封装为 SqLiteHelper，代码如下：

    /// <summary>
    /// SQLite 操作类
    /// </summary>
    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>
        /// <param name="value">关键字对应的值</param>
        /// <param name="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);
        }
    }

     Tips:1.别忘了引入：using System.Data.SQLite;

            2.引入System.Data.SQLite.dll的同时，需要将 System.Data.SQLite.dll.config 文件放在同级目录下。否则加载dll文件时报错。

    2.在工程主函数Main里面添加测试代码

class Program
    {
        private static SqLiteHelper sql;
        static void Main(string[] args)
        {
            sql = new SqLiteHelper("data source=mydb.db");
            
            
            //创建名为table1的数据表
            sql.CreateTable("table1", new string[] { "ID", "Name", "Age", "Email" }, new string[] { "INTEGER", "TEXT", "INTEGER", "TEXT" });
            //插入两条数据
            sql.InsertValues("table1",new string[]{"1","张三","22","Zhang@163.com" });
            sql.InsertValues("table1", 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("table1", 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("table1", new string[] { "Name", "Age" }, new string[] { "张三", "22" }, new string[] { "=", "=" });


            //读取整张表
            SQLiteDataReader reader = sql.ReadFullTable("table1");
            while (reader.Read())
            {
                //读取ID
                Log(""+reader.GetInt32(reader.GetOrdinal("ID")));
                //读取Name
                Log(""+reader.GetString(reader.GetOrdinal("Name")));
                //读取Age
                Log(""+reader.GetInt32(reader.GetOrdinal("Age")));
                //读取Email
                Log(reader.GetString(reader.GetOrdinal("Email")));
            }

            while (true)
            {
                Console.ReadLine();
            }
        }

        static void Log(string s)
        {
            Console.WriteLine(""+s);
        }
    }

    Tips:1.别忘了引入：using System.Data.SQLite;

    欢迎讨论！