C# SQLite 数据库

数据库

Oracle。Oracle的应用，主要在传统行业的数据化业务中，比如：银行、金融这样的对可用性、健壮性、安全性、实时性要求极高的业务

MS SQL Server。windows生态系统的产品，好处坏处都很分明。好处就是，高度集成化，微软也提供了整套的软件方案，基本上一套win系统装下来就齐活了。因此，不那么缺钱，但很缺IT人才的中小企业，会偏爱 MS SQL Server 。例如，自建ERP系统、商业智能、垂直领域零售商、餐饮、事业单位等等。

MySQL。MySQL基本是生于互联网，长于互联网。其应用实例也大都集中于互联网方向

SQLite介绍

SQLite，是一款轻型的数据库，是遵守ACID的关系型数据库管理系统，它包含在一个相对小的C库中。它的设计目标是嵌入式的，而且目前已经在很多嵌入式产品中使用了它，它占用资源非常的低，在嵌入式设备中，可能只需要几百K的内存就够了。

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#、PHP、Java等，还有ODBC接口。SQLite第一个Alpha版本诞生于2000年5月。 至2015年已经有15个年头。

Windows平台使用

1、在Assets目录下创建Plugins目录，将Mono.Data.Sqlite.dll、System.Data.dll、sqlite3.dll三个文件放到工程Plugins目录下。

2、在Assets目录下创建StreamingAssets目录，把db放在该目录内。

3、将DbAccess.cs脚本添加到工程中

Android平台使用

1、在Assets目录下创建Plugins目录，将Mono.Data.Sqlite.dll、System.Data.dll、sqlite3.dll三个文件放到工程Plugins目录下。

2、然后在Plugins目录下建立Android目录，再将libsqlite3.so放到Android目录下。

3、在Assets目录下创建StreamingAssets目录，把db放在该目录内。 4、将DbAccess.cs脚本添加到工程中。

 SQLite的数据库常规操作封装的通用类

using UnityEngine;
using System;
using System.Collections;
using Mono.Data.Sqlite;
/// <summary>
/// SQLite数据库操作类
/// </summary>
public class DbAccess
{
    private SqliteConnection conn; // SQLite连接
    private SqliteCommand cmd; // SQLite命令
    private SqliteDataReader reader;
    public DbAccess (string connectionString)    
    {
        OpenDB (connectionString);
    }
    public DbAccess (){ }
    /// <summary>
    /// 打开数据库
    /// </summary>
    /// <param name="connectionString"></param>
    public void OpenDB (string connectionString)        
    {
        try
        {
            conn = new SqliteConnection (connectionString);            
            conn.Open ();            
            Debug.Log ("Connected to db,连接数据库成功！");
        }
        catch(Exception e)
        {
            string temp1 = e.ToString();
            Debug.Log(temp1);
        }        
    }
    /// <summary>
    /// 关闭数据库连接
    /// </summary>
    public void CloseSqlConnection ()    
    {
        if (cmd != null) { cmd.Dispose (); cmd = null; }                        
        if (reader != null) { reader.Dispose (); reader = null;}                    
        if (conn != null) {    conn.Close (); conn = null;}            
        Debug.Log ("Disconnected from db.关闭数据库！");    
    }    
    /// <summary>
    /// 执行SQL语句
    /// </summary>
    /// <param name="sqlQuery"></param>
    /// <returns></returns>
    public SqliteDataReader ExecuteQuery ( string sqlQuery )        
    {
        Debug.Log( "ExecuteQuery:: " + sqlQuery );
        cmd = conn.CreateCommand ();
        cmd.CommandText = sqlQuery;
        reader = cmd.ExecuteReader ();
        return reader;
    }
    
    /// <summary>
    /// 查询表中全部数据 param tableName=表名 
    /// </summary>
    public SqliteDataReader ReadFullTable (string tableName)        
    {
        string query = "SELECT * FROM " + tableName;
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 插入数据 param tableName=表名 values=插入数据内容
    /// </summary>
    public SqliteDataReader InsertInto (string tableName, string[] values)        
    {
        string query = "INSERT INTO " + tableName + " VALUES (" + values[0];
        for (int i = 1; i < values.Length; ++i) {    
            query += ", " + values[i];    
        }
        query += ")";
        return ExecuteQuery (query);
    }    
    /// <summary>
    /// 更新数据 param tableName=表名 cols=更新字段 colsvalues=更新内容 selectkey=查找字段（主键) selectvalue=查找内容
    /// </summary>
    public SqliteDataReader UpdateInto (string tableName, string []cols,string []colsvalues,string selectkey,string selectvalue)
    {
        string query = "UPDATE "+tableName+" SET "+cols[0]+" = "+colsvalues[0];
        for (int i = 1; i < colsvalues.Length; ++i) {
            query += ", " +cols[i]+" ="+ colsvalues[i];
        }        
        query += " WHERE "+selectkey+" = "+selectvalue+" ";        
        return ExecuteQuery (query);
    }
    
    /// <summary>
    /// 删除数据 param tableName=表名 cols=字段 colsvalues=内容
    /// </summary>
    public SqliteDataReader Delete(string tableName,string []cols,string []colsvalues)
    {
        string query = "DELETE FROM "+tableName + " WHERE " +cols[0] +" = " + colsvalues[0];        
        for (int i = 1; i < colsvalues.Length; ++i) {            
            query += " or " +cols[i]+" = "+ colsvalues[i];
        }
        return ExecuteQuery (query);
    }    
    /// <summary>
    /// 插入数据 param tableName=表名 cols=插入字段 value=插入内容
    /// </summary>
    public SqliteDataReader InsertIntoSpecific (string tableName, string[] cols, string[] values)        
    {
        if (cols.Length != values.Length) {    
            throw new SqliteException ("columns.Length != values.Length");
        }
        string query = "INSERT INTO " + tableName + "(" + cols[0];
        for (int i = 1; i < cols.Length; ++i) {    
            query += ", " + cols[i];    
        }
        query += ") VALUES (" + values[0];
        for (int i = 1; i < values.Length; ++i) {    
            query += ", " + values[i];    
        }        
        query += ")";        
        return ExecuteQuery (query);        
    }
    /// <summary>
    /// 删除表中全部数据
    /// </summary>
    public SqliteDataReader DeleteContents (string tableName)        
    {    
        string query = "DELETE FROM " + tableName;
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 创建表 param name=表名 col=字段名 colType=字段类型
    /// </summary>
    public SqliteDataReader CreateTable (string name, string[] col, string[] colType)
    {
        if (col.Length != colType.Length) {
            throw new SqliteException ("columns.Length != colType.Length");
        }
        string query = "CREATE TABLE " + name + " (" + col[0] + " " + colType[0];        
        for (int i = 1; i < col.Length; ++i) {    
            query += ", " + col[i] + " " + colType[i];    
        }
        query += ")";        
        return ExecuteQuery (query);        
    }
    /// <summary>
    /// 按条件查询数据 param tableName=表名 items=查询字段 col=查找字段 operation=运算符 values=内容
    /// </summary>
    public SqliteDataReader SelectWhere (string tableName, string[] items, string[] col, string[] operation, string[] values)    
    {    
        if (col.Length != operation.Length || operation.Length != values.Length) {    
            throw new SqliteException ("col.Length != operation.Length != values.Length");    
        }
        string query = "SELECT " + items[0];
        for (int i = 1; i < items.Length; ++i) {    
            query += ", " + items[i];
        }
        query += " FROM " + tableName + " WHERE " + col[0] + operation[0] + "'" + values[0] + "' ";
        for (int i = 1; i < col.Length; ++i) {
            query += " AND " + col[i] + operation[i] + "'" + values[i] + "' ";
        }
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 查询表
    /// </summary>
    public SqliteDataReader Select(string tableName, string col, string values)
    {
        string query = "SELECT * FROM " + tableName  + " WHERE " + col + " = " + values;
        return ExecuteQuery (query);
    }
    public SqliteDataReader Select(string tableName, string col,string operation, string values)
    {
        string query = "SELECT * FROM " + tableName  + " WHERE " + col + operation + values;
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 升序查询
    /// </summary>
    public SqliteDataReader SelectOrderASC (string tableName,string col)
    {
        string query = "SELECT * FROM " + tableName  + " ORDER BY " + col + " ASC";
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 降序查询
    /// </summary>
    public SqliteDataReader SelectOrderDESC (string tableName,string col)
    {
        string query = "SELECT * FROM " + tableName  + " ORDER BY " + col + " DESC";
        return ExecuteQuery (query);
    }
    /// <summary>
    /// 查询表行数
    /// </summary>
    public SqliteDataReader SelectCount(string tableName)
    {
        string query = "SELECT COUNT(*) FROM " + tableName;
        return ExecuteQuery (query);
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Mono .Data .Sqlite;

namespace ns
{
    /// <summary>
    ///  打开和关闭数据库
    /// </summary>
    public class SQLiteHelper : MonoBehaviour 
    {
        protected string dbName = "test2.db"; // 文件名
        private string filePath // 文件路径
        {
            get { return Application .streamingAssetsPath + "/" + dbName; }
        }

        protected DbAccess db; // dbAccess实例
        protected SqliteDataReader reader;// 
        /// <summary>
        /// 打开数据库
        /// </summary>
        protected void OpenDB()
        {
            db = new DbAccess( "URI=file:" + filePath );
        }
        /// <summary>
        /// 关闭数据库
        /// </summary>
        protected void CloseDB()
        {
            if( reader != null )
            {
                reader .Close();
                reader = null;
            }
            
            db .CloseSqlConnection();
        }
        /// <summary>
        /// 对象前后添加单引号
        /// </summary>
        /// <param name="o"></param>
        /// <returns></returns>
        protected string GetStr( object o )
        {
            return "'" + o + "'";
        }

    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using ns;

public class MySQLiteDemo : MySQLiteHelper
{
    /// <summary>
    /// 创建表
    /// </summary>
    private void CreateTable()
    {
        //打开数据库
        OpenDB();

        db.CreateTable("MyRole", new string[] { "id", "name", "age", "lv", "exp" },
            new string[] { "int", "text", "int", "int", "float" });
        //关闭数据库
        CloseDB();
    }


    /// <summary>
    /// 插入数据
    /// </summary>
    private void InsertData()
    {
        //打开数据库
        OpenDB();
        //插入数据库
        db.InsertInto
            ("MyRole", new string[] { GetStr("1"), GetStr("张三"), GetStr("100"), GetStr("12"), GetStr("120") });
        db.InsertInto
            ("MyRole", new string[] { GetStr("2"), GetStr("李四"), GetStr("110"), GetStr("13"), GetStr("130") });
        db.InsertInto
            ("MyRole", new string[] { GetStr("3"), GetStr("王五"), GetStr("120"), GetStr("14"), GetStr("140") });
        db.InsertInto
            ("MyRole", new string[] { GetStr("4"), GetStr("赵六"), GetStr("130"), GetStr("15"), GetStr("150") });

        //关闭数据库
        CloseDB();
    }

    /// <summary>
    /// 删除数据库
    /// </summary>
    private void DeleteData()
    {
        //打开数据库
        OpenDB();
        // 删除数据: 多个条件直接是或的关系
        // DELETE FROM Role WHERE id = 1 or lv = 13

        //db.Delete("MyRole",
        //    new string[] { "id", "lv" },
        //    new string[] { "1", "130" }
        //    );
        db.DeleteContents("MyRole");
        //关闭数据库

        CloseDB();
    }
    /// <summary>
    /// 更新数据
    /// </summary>
    private void UpdateData()
    {
        //打开数据库
        OpenDB();
        // 更新数据: id为1数据 exp改为350 lv改为16
        // UPDATE Role SET exp = 350, lv =16 WHERE id = 1 
        db.UpdateInto("MyRole", 
            new string[] { "exp", "lv" }, new string[] { "350", "16", }, "id", "1");
        //关闭数据库
        CloseDB();
    }
    // 查找数据
    private void SearchData()
    {
        OpenDB();
        // 查询 查找id为3 lv为21的数据
        // 找到 name 和 age
        // 多个条件之间是与的关系
        // SELECT name, age FROM Role WHERE id='3'  AND lv='14'
        reader = db.SelectWhere("MyRole",
            new string[] { "name", "age" },
            new string[] { "id", "lv" },
            new string[] { "=", "=" },
            new string[] { "1", "14" }
            );
        if (reader.HasRows)
        {
            reader.Read();
            print(reader.GetString(reader.GetOrdinal("name")));
            print(reader.GetInt32(reader.GetOrdinal("age")));
        }

        CloseDB();
    }

    /// <summary>
    /// 查找多个数据
    /// </summary>
    private void SelectData()
    {
       // 打开数据库
            OpenDB();

            //reader = db .Select( "Role" , "id" , "2" );// 查询所有id 为 2的数据
            //reader = db .Select( "Role" , "id" , ">" , "1" ); // 查询所有id>1的数据
            //reader = db .ReadFullTable("Role"); // 读取整张表 
            //reader = db .SelectOrderASC( "Role" , "age" ); // age从小到大排列
            reader = db .SelectOrderDESC( "MyRole" , "lv" ); //  lv从大到小
            if ( reader.HasRows )
            {
                while( reader .Read() )
                {
                    string s = "";
                    s += reader .GetInt32( reader .GetOrdinal( "id" ) ) + " , " ;
                    s += reader .GetString( reader .GetOrdinal( "name" ) ) + " , ";
                    s += reader .GetInt32( reader .GetOrdinal( "age" ) ) + " , ";
                    s += reader .GetInt32( reader .GetOrdinal( "lv" ) ) + " , ";
                    s += reader .GetFloat( reader .GetOrdinal( "exp" ) );
                    print( s );
                }
            }
            // 关闭数据库
            CloseDB();
    }

    private void OnGUI()
    {
        if (GUILayout.Button("创建MyRole表"))
        {
            CreateTable();
        }
        if (GUILayout.Button("插入数据"))
        {
            InsertData();
        }
        if (GUILayout.Button("删除数据库"))
        {
            DeleteData();
        }
        if (GUILayout.Button("更新数据"))
        {
            UpdateData();
        }
        if (GUILayout.Button("查询数据"))
        {
            SearchData();
        }
        if (GUILayout.Button("多条数据查询"))
        {
            SelectData();
        }
    }


}