Delete Data

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Deleting data is a very dangerous operation. FreeSql does not support deletion very powerfully. By default, it only supports single-table and conditional deletion methods.

If it is executed when the Where condition is empty, only 0 or the default value is returned, and no real SQL delete operation is performed.

static IFreeSql fsql = new FreeSql.FreeSqlBuilder()
    .UseConnectionString(FreeSql.DataType.MySql, connectionString)
    .UseAutoSyncStructure(true) //Automatically synchronize the entity structure to the database
    .Build(); //Be sure to define as singleton mode

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; }
}

Dynamic Conditions

fsql.Delete<Topic>(object dywhere)

dywhere supports:

• Primary key value
• new[] { 主键值1, 主键值2 }
• Topic Object
• new[] { TopicObject1, TopicObject2 }
• 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` = 1 OR `Id` = 2)

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

Delete Conditions

For safety reasons, when there are no conditions, the delete action will not be executed to avoid deleting the entire table data by mistake. Delete the entire table data: 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))

ISelect.ToDelete Advanced Delete

IDelete does not support navigation objects, multi-table association, etc. By default, ISelect.ToDelete can convert the query to IDelete so that the navigation object can be used to delete data:

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

Note: This method is not to query the data to the memory and delete it cyclically. The above code generates and executes the following SQL:

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)

The benefits of using this method for complex deletion:

• Preview data before deleting to prevent mistaken deletion operations;
• Support complex deletion operations, for example: Use Limit(10) on ISelect to delete the first 10 records that meet the conditions;

Reference

• 《Database Transaction》
• 《FreeSql 101, Part 1: Insert Data》
• 《FreeSql 101, Part 3: Update Data》
• 《FreeSql 101, Part 4: Query Data》
• 《Repository Layer》
• 《Tenant》

API

Methods	Return	Parameters	Description
Where	<this>	Lambda	Expression conditions, only support entity basic members (not including navigation objects)
Where	<this>	string, parms	Raw SQL syntax conditions, Where("id = @id", new { id = 1 })
Where	<this>	T1 | IEnumerable<T1>	Pass in the entity or collection, and use its primary key as the condition
CommandTimeout	<this>	int	Command timeout setting (seconds)
WithTransaction	<this>	DbTransaction	Set transaction object
WithConnection	<this>	DbConnection	Set the connection object
ToSql	string		Returns the SQL statement to be executed.
ExecuteAffrows	long		Execute SQL and return the number of rows affected.
ExecuteDeleted	List<T1>		Execute SQL and return the deleted records.