后台代码的SQL语句根据不同数据库转换

一般情况下，我们的SQL语句都写在代码里，虽然耦合度高了，但是方便。然而，如果突然有一天，需求变了，换数据库，然后我们用新的数据库，一调试，发现有些SQL语句不执行，傻眼了，只能一条一条的改，而且，如果有一天数据库又要换回来，又要改回去，非常不方便。这里我提供一个方法。

根据配置更换数据库

关键词ProviderName

Aceess数据库 System.Data.OleDb
SQLite数据库 System.Data.SQLite
Oracle 数据库 System.Data.OracleClient 或 Oracle.DataAccess.Client
MySql数据库 MySql.Data.MySqlClient

原本代码

我原本使用Sqlite数据库的代码

public static IDbConnection GetDBConnection()
{
	System.Data.SQLite.SQLiteConnectionStringBuilder SQLiteSB = new System.Data.SQLite.SQLiteConnectionStringBuilder();
	SQLiteSB.DataSource = System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ConnectionString;
	return new System.Data.SQLite.SQLiteConnection(SQLiteSB.ToString());
}

使用Access数据库的代码

public static IDbConnection GetDBConnection()
{
	System.Data.OleDb.OleDbConnectionStringBuilder AccessSB = new System.Data.OleDb.OleDbConnectionStringBuilder();
	AccessSB.Provider = "Microsoft.ACE.OLEDB.12.0";
	AccessSB.DataSource = System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ConnectionString;
	return new System.Data.OleDb.OleDbConnection(AccessSB.ToString());
}

更改之后的代码

修改为一个抽象类MyDb

public abstract class MyDb
{
    private static MyDb _myDb;
    public abstract IDbConnection GetDbConnection();
    public abstract string InsertTest();
    public string SelectMyProject_All()
    {
        return "select * from MyProject where Name = @Name";
    }
    public string InsertMyProject()
    {
        return "insert into MyProject(ProjectID,Name,SharpType) Values(@ProjectID,@Name,@SharpType)";
    }
    public string InsertMySharp()
    {
        return "insert into MySharp(ProjectID,Name,SharpID) Values(@ProjectID,@Name,@SharpID)";
    }
    public string InsertProperty()
    {
        return "insert into Property(Standard,PositiveTolerance,NegativeTolerance,Compensation,PropertyID,Name,SharpID,IsSelected) Values(@Standard,@PositiveTolerance,@NegativeTolerance,@Compensation,@PropertyID,@Name,@SharpID,@IsSelected)";
    }
    public string SelectMyProject_ProjectForm()
    {
        return "select t1.projectID as ProjectIDString,t1.Name,t1.Selection,t2.Name as SharpName from MyProject t1 left join MySharp t2 on t1.ProjectID=t2.ProjectID"; ;
    }
    public string SelectProperty()
    {
        return "select t1.Standard,t1.NegativeTolerance,t1.PositiveTolerance,t1.Compensation,t1.PropertyID as PropertyIDString,t1.IsSelected,t1.Name,t1.SharpID as SharpIDString from Property t1 left join MySharp t2 on t1.SharpID=t2.SharpID where t2.ProjectID=@ProjectID";
    }
    public string DelectMyProject()
    {
        return "delete from MyProject where Name =@Name";
    }
    public static MyDb CreateMyDbFactory()
    {
        switch (System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ProviderName)
        {
            //Aceess数据库
            case "System.Data.OleDb":
                _myDb = new AccessDb();
                return _myDb;

            //SQLite数据库
            case "System.Data.SQLite":
            default:
                _myDb = new SqliteDb();
                return _myDb;
                Oracle 数据库
                //case "System.Data.OracleClient":
                //case "Oracle.DataAccess.Client":
                //    break;
                MySql数据库
                //case "MySql.Data.MySqlClient":
                //    break;
        }
    }
}

一个Access的类继承MyDb

public class AccessDb : MyDb
{
    public override IDbConnection GetDbConnection()
    {
        System.Data.OleDb.OleDbConnectionStringBuilder AccessSB = new System.Data.OleDb.OleDbConnectionStringBuilder();
        AccessSB.Provider = "Microsoft.ACE.OLEDB.12.0";
        AccessSB.DataSource = System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ConnectionString;
        return new System.Data.OleDb.OleDbConnection(AccessSB.ToString());
    }

    public override string InsertTest()
    {
        return "insert into Test([ID],[TestID],[PropertyID],[Name],[Value],[IsMore],[IsLess]) Values(@ID,@TestID,@PropertyID,@Name,@Value,@IsMore,@IsLess)";
    }
}

一个Sqlite的类继承MyDb

public class SqliteDb : MyDb
{
    public override IDbConnection GetDbConnection()
    {
        System.Data.SQLite.SQLiteConnectionStringBuilder SQLiteSB = new System.Data.SQLite.SQLiteConnectionStringBuilder();
        SQLiteSB.DataSource = System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ConnectionString;
        return new System.Data.SQLite.SQLiteConnection(SQLiteSB.ToString());
    }

    public override string InsertTest()
    {
        return "insert into Test(ID,TestID,PropertyID,Name,Value,IsMore,IsLess) Values(@ID,@TestID,@PropertyID,@Name,@Value,@IsMore,@IsLess)";
    }
}

后台代码调用

之前的SQL语句代码

using (System.Data.IDbConnection con = db.GetDbConnection())
{
    string sqlStr = "insert into Test([ID],[TestID],[PropertyID],[Name],[Value],[IsMore],[IsLess]) Values(@ID,@TestID,@PropertyID,@Name,@Value,@IsMore,@IsLess)";
    con.Execute(sqlStr, new
    {
        ID = test.ID.ToString("N"),
        TestID = test.TestID.ToString("N"),
        PropertyID = test.PropertyID.ToString("N"),
        Name = test.Name,
        Value = values,
        IsMore = test.IsMore,
        IsLess = test.IsLess,
        Time = test.Time
    });
}

改了之后

var db = MyDb.CreateMyDbFactory();
using (System.Data.IDbConnection con = db.GetDbConnection())
{
    string sqlStr = db.InsertTest();
    con.Execute(sqlStr, new
    {
        ID = test.ID.ToString("N"),
        TestID = test.TestID.ToString("N"),
        PropertyID = test.PropertyID.ToString("N"),
        Name = test.Name,
        Value = values,
        IsMore = test.IsMore,
        IsLess = test.IsLess,
        Time = test.Time
    });
}

改成MyDb抽象类之后便于测试，把SQL语句统一放在一个类里方便管理，而且耦合度低，还符合单一职责。

移植出业务逻辑层中的数据访问层的东西

后来，我看了三层架构，发现业务代码里，虽然SQL语句被隐藏了，但是还是有对数据进行操作，应该隐藏起来，如果要改，还是在数据访问层操作比较好。于是把MyDb类改成如下所示，将之前的得到SQL语句的方法变为protected。

    public abstract class MyDb
    {
        private static MyDb _myDb;
        protected abstract IDbConnection GetDbConnection();
        protected abstract string CreateTest();
        protected abstract string RetrieveTest();
        protected string RetrieveMyProject_All()
        {
            return "select * from MyProject where Name = @Name";
        }
        protected string CreateMyProject()
        {
            return "insert into MyProject(ProjectID,Name,SharpType) Values(@ProjectID,@Name,@SharpType)";
        }
        protected string CreateMySharp()
        {
            return "insert into MySharp(ProjectID,Name,SharpID) Values(@ProjectID,@Name,@SharpID)";
        }
        protected string CreateProperty()
        {
            return "insert into Property(Standard,PositiveTolerance,NegativeTolerance,Compensation,PropertyID,Name,SharpID,IsSelected) Values(@Standard,@PositiveTolerance,@NegativeTolerance,@Compensation,@PropertyID,@Name,@SharpID,@IsSelected)";
        }
        protected string RetrieveMyProject_ProjectForm()
        {
            return "select t1.projectID as ProjectIDString,t1.Name,t1.Selection,t2.Name as SharpName from MyProject t1 left join MySharp t2 on t1.ProjectID=t2.ProjectID"; ;
        }
        protected string RetrieveProperty()
        {
            return "select t1.Standard,t1.NegativeTolerance,t1.PositiveTolerance,t1.Compensation,t1.PropertyID as PropertyIDString,t1.IsSelected,t1.Name,t1.SharpID as SharpIDString from Property t1 left join MySharp t2 on t1.SharpID=t2.SharpID where t2.ProjectID=@ProjectID";
        }
        protected string DelectMyProject()
        {
            return "delete from MyProject where Name =@Name";
        }
        #region 公有方法
        public virtual int CreateTest(ITest test)
        {
            string values = string.Empty;
            foreach (double dd in test.Value)
            {
                values += dd + ",";
            }
            values = values.Remove(values.Length - 1);
            using (System.Data.IDbConnection con = GetDbConnection())
            {
                //string sqlStr = "insert into Test([ID],[TestID],[PropertyID],[Name],[Value],[IsMore],[IsLess]) Values(@ID,@TestID,@PropertyID,@Name,@Value,@IsMore,@IsLess)";
                string sqlStr = CreateTest();
                return con.Execute(sqlStr, new
                {
                    ID = test.ID.ToString("N"),
                    TestID = test.TestID.ToString("N"),
                    PropertyID = test.PropertyID.ToString("N"),
                    Name = test.Name,
                    Value = values,
                    IsMore = test.IsMore,
                    IsLess = test.IsLess,
                    Time = test.Time
                });
            }
        }
        public int CreateMyProject(MyProject myProject)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //string sqlStr = "insert into MyProject(ProjectID,Name,SharpType) Values(@ProjectID,@Name,@SharpType)";
                string sqlStr = CreateMyProject();
                return con.Execute(sqlStr, new { ProjectID = myProject.ProjectID.ToString("N"), Name = myProject.Name, SharpType = myProject.SharpType });
            }
        }
        public int RetrieveMyProject_All(string name)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //string sqlStr = "select * from MyProject where Name = @Name";
                string sqlStr = RetrieveMyProject_All();
                return con.Query(sqlStr, new { Name = name }).Count();
            }
        }
        public int CreateMySharp(MyProject myProject)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //sqlStr = "insert into MySharp(ProjectID,Name,SharpID) Values(@ProjectID,@Name,@SharpID)";
                string sqlStr = CreateMySharp();
                return con.Execute(sqlStr, new { ProjectID = myProject.MySharp.ProjectID.ToString("N"), Name = myProject.MySharp.Name, SharpID = myProject.MySharp.SharpID.ToString("N") });
            }
        }
        public int CreateProperty(Property property)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //sqlStr = "insert into Property(Standard,PositiveTolerance,NegativeTolerance,Compensation,PropertyID,Name,SharpID,IsSelected) Values(@Standard,@PositiveTolerance,@NegativeTolerance,@Compensation,@PropertyID,@Name,@SharpID,@IsSelected)";
                string sqlStr = CreateProperty();
                return con.Execute(sqlStr, new
                {
                    Standard = property.Standard,
                    PositiveTolerance = property.PositiveTolerance,
                    NegativeTolerance = property.NegativeTolerance,
                    Compensation = property.Compensation,
                    PropertyID = property.PropertyID.ToString("N"),
                    Name = property.Name,
                    SharpID = property.SharpID.ToString("N"),
                    IsSelected = property.IsSelected
                });
            }
        }
        public List RetrieveMyProject_ProjectForm(object param = null)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //string sqlStr = "select t1.projectID as ProjectIDString,t1.Name,t1.Selection,t2.Name as SharpName from MyProject t1 left join MySharp t2 on t1.ProjectID=t2.ProjectID";
                string sqlStr = RetrieveMyProject_ProjectForm();
                return con.Query(sqlStr).ToList();
            }
        }
        public List RetrieveProperty(MyProject myProject)
        {
            using (IDbConnection con = GetDbConnection())
            {
                string sqlStr = RetrieveProperty();
                //string sqlStr = "select t1.Standard,t1.NegativeTolerance,t1.PositiveTolerance,t1.Compensation,t1.PropertyID as PropertyIDString,t1.IsSelected,t1.Name,t1.SharpID as SharpIDString from Property t1 left join MySharp t2 on t1.SharpID=t2.SharpID where t2.ProjectID=@ProjectID";
                return con.Query(sqlStr, new { ProjectID = myProject.ProjectID.ToString("N") }).Select(PropertyHelper.ConvertToProperty).ToList();
            }
        }
        public int DelectMyProject(MyProject myProject)
        {
            using (IDbConnection con = GetDbConnection())
            {
                //string sqlStr = "delete from MyProject where Name =@Name";
                string sqlStr = DelectMyProject();
                return con.Execute(sqlStr, myProject);
            }
        }
        public DataTable RetrieveTest(object param = null)
        {
            using (IDbConnection con = GetDbConnection())
            {
                return DBHelper.ToDataTable(con.Query(RetrieveTest()));
            }
        }
        public static MyDb CreateMyDbFactory()
        {
            switch (System.Configuration.ConfigurationManager.ConnectionStrings["dbPath"].ProviderName)
            {
                //Aceess数据库
                case "System.Data.OleDb":
                    _myDb = new AccessDb();
                    return _myDb;

                //SQLite数据库
                case "System.Data.SQLite":
                default:
                    _myDb = new SqliteDb();
                    return _myDb;
                    Oracle 数据库
                    //case "System.Data.OracleClient":
                    //case "Oracle.DataAccess.Client":
                    //    break;
                    MySql数据库
                    //case "MySql.Data.MySqlClient":
                    //    break;
            }
        }
        #endregion
    }

外部调用

public class TestFactory : ITestFactory
{
	private readonly MyDb _myDb;
	private ITest test;
	public Guid TestID { get; set; }
	public TestFactory() : this(MyDb.CreateMyDbFactory()) { }
	
	internal TestFactory(MyDb myDb)
	{
	    this._myDb = myDb;
	}
	public ITest CreateTest()
	{
		//test的相关操作
		_myDb.CreateTest(test);
		return test;
	}
}

如果有什么其他方法或者觉得我不对的地方，请不吝指出。