删除

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删除是一个非常危险的操作，FreeSql 对删除支持并不强大，默认仅支持单表、且有条件的删除方法。

若 Where 条件为空的时候执行，仅返回 0 或默认值，不执行真正的 SQL 删除操作。

static IFreeSql fsql = new FreeSql.FreeSqlBuilder()
    .UseConnectionString(FreeSql.DataType.MySql, connectionString)
    .UseAutoSyncStructure(true) //自动同步实体结构到数据库
    .Build(); //请务必定义成 Singleton 单例模式

class Topic {
    [Column(IsIdentity = true, IsPrimary = true)]
    public int Id { get; set; }
    public int Clicks { get; set; }
    public string Title { get; set; }
    public DateTime CreateTime { get; set; }
}

动态条件

fsql.Delete<Topic>(object dywhere)

dywhere 支持：

• 主键值
• new[] { 主键值1, 主键值2 }
• Topic 对象
• new[] { Topic对象1, Topic对象2 }
• new { id = 1 }

var t1 = fsql.Delete<Topic>(new[] { 1, 2 }).ToSql();
//DELETE FROM `Topic` WHERE (`Id` = 1 OR `Id` = 2)

var t2 = fsql.Delete<Topic>(new Topic { Id = 1, Title = "test" }).ToSql();
//DELETE FROM `Topic` WHERE (`Id` = 1)

var t3 = fsql.Delete<Topic>(new[] { new Topic { Id = 1, Title = "test" }, new Topic { Id = 2, Title = "test" } }).ToSql();
//DELETE FROM `Topic` WHERE (`Id` in (1, 2))

var t4 = fsql.Delete<Topic>(new { id = 1 }).ToSql();
//DELETE FROM `Topic` WHERE (`Id` = 1)

删除条件

出于安全考虑，没有条件不执行删除动作，避免误删除全表数据。删除全表数据：fsql.Delete<T>().Where("1=1").ExecuteAffrows()

var t5 = fsql.Delete<Topic>().Where(a => a.Id == 1).ToSql();
//DELETE FROM `Topic` WHERE (`Id` = 1)

var t6 = fsql.Delete<Topic>().Where("id = @id", new { id = 1 }).ToSql();
//DELETE FROM `Topic` WHERE (id = @id)

var item = new Topic { Id = 1, Title = "newtitle" };
var t7 = fsql.Delete<Topic>().Where(item).ToSql();
//DELETE FROM `Topic` WHERE (`Id` = 1)

var items = new List<Topic>();
for (var a = 0; a < 10; a++) items.Add(new Topic { Id = a + 1, Title = $"newtitle{a}", Clicks = a * 100 });
var t8 = fsql.Delete<Topic>().Where(items).ToSql();
//DELETE FROM `Topic` WHERE (`Id` IN (1,2,3,4,5,6,7,8,9,10))

字典删除

var dic = new Dictionary<string, object>();
dic.Add("id", 1);
dic.Add("name", "xxxx");

fsql.DeleteDict(dic).AsTable("table1").ExecuteAffrows();

ISelect.ToDelete 高级删除

IDelete 默认不支持导航对象，多表关联等。ISelect.ToDelete 可将查询转为 IDelete，以便使用导航对象删除数据，如下：

fsql.Select<T1>().Where(a => a.Options.xxx == 1).ToDelete().ExecuteAffrows();

注意：此方法不是将数据查询到内存循环删除，上面的代码产生如下 SQL 执行：

DELETE FROM `T1` WHERE id in (select a.id from T1 a left join Options b on b.t1id = a.id where b.xxx = 1)

复杂删除使用此方法的好处：

• 删除前可预览测试数据，防止错误删除操作；
• 支持复杂的删除操作，例如：ISelect 上使用 Limit(10) 删除附合条件的前 10 条记录；

IBaseRepository 级联删除

1、第一种：基于【对象】级联删除

比如 Include/IncludeMany 查询的对象，可以使用此方法级联删除它们。

var repo = fsql.GetRepository<Group>();
repo.DbContextOptions.EnableCascadeSave = true; //关键设置
repo.Insert(new UserGroup
{
    GroupName = "group01",
    Users = new List<User>
    {
        new User { Username = "admin01", Password = "pwd01", UserExt = new UserExt { Remark = "用户备注01" } },
        new User { Username = "admin02", Password = "pwd02", UserExt = new UserExt { Remark = "用户备注02" } },
        new User { Username = "admin03", Password = "pwd03", UserExt = new UserExt { Remark = "用户备注03" } },
    }
}); //级联添加测试数据
//INSERT INTO "usergroup"("groupname") VALUES('group01') RETURNING "id"
//INSERT INTO "user"("username", "password", "groupid") VALUES('admin01', 'pwd01', 1), ('admin02', 'pwd02', 1), ('admin03', 'pwd03', 1) RETURNING "id" as "Id", "username" as "Username", "password" as "Password", "groupid" as "GroupId"
//INSERT INTO "userext"("userid", "remark") VALUES(3, '用户备注01'), (4, '用户备注02'), (5, '用户备注03')

var groups = repo.Select
    .IncludeMany(a => a.Users, 
        then => then.Include(b => b.UserExt))
    .ToList();
repo.Delete(groups); //级联删除，递归向下遍历 group OneToOne/OneToMany/ManyToMany 导航属性
//DELETE FROM "userext" WHERE ("userid" IN (3,4,5))
//DELETE FROM "user" WHERE ("id" IN (3,4,5))
//DELETE FROM "usergroup" WHERE ("id" = 1)

2、第二种：基于【数据库】级联删除

根据设置的导航属性，递归删除 OneToOne/OneToMany/ManyToMany 对应数据，并返回已删除的数据。此功能不依赖数据库外键

var repo = fsql.GetRepository<Group>();
var ret = repo.DeleteCascadeByDatabase(a => a.Id == 1);
//SELECT a."id", a."username", a."password", a."groupid" FROM "user" a WHERE (a."groupid" = 1)
//SELECT a."userid", a."remark" FROM "userext" a WHERE (a."userid" IN (3,4,5))
//DELETE FROM "userext" WHERE ("userid" IN (3,4,5))
//DELETE FROM "user" WHERE ("id" IN (3,4,5))
//DELETE FROM "usergroup" WHERE ("id" = 1)

//ret   Count = 7	System.Collections.Generic.List<object>
//  [0]	{UserExt}	object {UserExt}
//  [1]	{UserExt}	object {UserExt}
//  [2]	{UserExt}	object {UserExt}
//  [3]	{User}	    object {User}
//  [4]	{User}	    object {User}
//  [5]	{User}  	object {User}
//  [6]	{UserGroup}	object {UserGroup}

public class Group
{
    [Column(IsIdentity = true)]
    public int Id { get; set; }
    public string GroupName { get; set; }

    [Navigate(nameof(User.GroupId))]
    public List<User> Users { get; set; }
}
public class User
{
    [Column(IsIdentity = true)]
    public int Id { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public int GroupId { get; set; }

    [Navigate(nameof(Id))]
    public UserExt UserExt { get; set; }
}
public class UserExt
{
    [Column(IsPrimary = true)]
    public int UserId { get; set; }
    public string Remark { get; set; }

    [Navigate(nameof(UserId))]
    public User User { get; set; }
}

参考资料

• 《数据库事务》
• 《学习FreeSql之一：添加数据》
• 《学习FreeSql之二：修改数据》
• 《学习FreeSql之三：查询数据》
• 《仓储层Repository》
• 《租户》

API

方法	返回值	参数	描述
Where	<this>	Lambda	表达式条件，仅支持实体基础成员（不包含导航对象）
Where	<this>	string, parms	原生sql语法条件，Where("id = @id", new { id = 1 })
Where	<this>	T1 | IEnumerable<T1>	传入实体或集合，将其主键作为条件
CommandTimeout	<this>	int	命令超时设置(秒)
WithTransaction	<this>	DbTransaction	设置事务对象
WithConnection	<this>	DbConnection	设置连接对象
ToSql	string		返回即将执行的SQL语句
ExecuteAffrows	long		执行SQL语句，返回影响的行数
ExecuteDeleted	List<T1>		执行SQL语句，返回被删除的记录