How to cascade-delete temporarily or on-demand?

Question

Sometimes I'm trying to delete just ONE row in MSSQL and I fall into countless deletes up the hierarchy because of references due to foreign-key constraints. Is there any quick way to automatically cascade-delete without having to setup the foreign-key constraints with cascade delete? It's just this one time that I need the cascade-delete... on-demand -- not always.

Any chance? Any equivalents?

Answer 1

If you want a point and shoot dynamic sql solution, this uses a recursive query to build a table hierarchy for foreign keys that descends from a particlar key. With that it generates the delete statements that need to be executed, in order (hopefully), to delete a particular row from a table.

use AdventureWorks2012

declare @tablename sysname = N'Production.Product';
declare @primarykeycolumn sysname = N'ProductId';
declare @value nvarchar(128) = '2';
declare @sql nvarchar(max);

;with tableHierarchy as (
select
    object_id = p.object_id
  , parent_id = cast(null as int)
  , schemaName = schema_name(p.schema_id)
  , tableName = object_name(p.object_id)
  , parentObjectName = cast(null as sysname)
  , parentToChild = cast(object_name(p.object_id) as varchar(max))
  , childToParent = cast(object_name(p.object_id) as varchar(max))
  , treelevel = 0
  , keyName = p.name
  , columnName = c.name
  , columnId = c.column_id
  , parentColumnName = c.name
from sys.objects as p
  inner join sys.columns c
    on p.object_id = c.object_id
where p.object_id  = object_id(@tablename)
  and c.name = @primarykeycolumn
union all
select
    object_id = fk.parent_object_id
  , parent_id = fk.referenced_object_id
  , schemaName = schema_name(fk.schema_id)
  , tableName = object_name(fk.parent_object_id)
  , parentObjectName = object_name(fk.referenced_object_id)
  , parentToChild = parentToChild + ' \ ' + cast(object_name(fk.parent_object_id) as varchar(128))
  , childToParent = cast(object_name(fk.parent_object_id) as varchar(128)) + ' \ ' + childToParent
  , treelevel = th.treelevel + 1
  , keyName = fk.name
  , columnName = c.name
  , columnId = c.column_id
  , parentColumnName = rc.name
from tableHierarchy as th
  inner join sys.foreign_keys as fk
    on fk.referenced_object_id = th.object_id
   and fk.referenced_object_id != fk.parent_object_id 
  inner join sys.foreign_key_columns fkc
    on fk.object_id = fkc.constraint_object_id
  and fkc.referenced_column_id = th.columnId
  inner join sys.columns c
    on fkc.parent_object_id = c.object_id
   and fkc.parent_column_id = c.column_id
  inner join sys.columns rc
    on fkc.referenced_object_id = rc.object_id
   and fkc.referenced_column_id = rc.column_id
)
select @sql = stuff((
  select 
      char(10)
    --+'/* treelevel: '+convert(nvarchar(10),treelevel)
    --+' | ' + childtoparent +' */'+char(10)
    +'delete from '+quotename(schemaName)+'.'+quotename(tableName)
    +' where '+quotename(columnName)+' = '+@value+';'
  from tableHierarchy
  group by treelevel, childtoparent, schemaName, tableName, columnName
  order by treelevel desc, childtoparent
  for xml path (''), type).value('.','nvarchar(max)')
  ,1,1,'')
  option ( maxrecursion 100 );

select @sql as CodeGenerated;
--exec sp_executesql @sql;

Code generated:

delete from [Sales].[SalesOrderDetail] where [ProductID] = 2;
delete from [Production].[BillOfMaterials] where [ComponentID] = 2;
delete from [Production].[BillOfMaterials] where [ProductAssemblyID] = 2;
delete from [Production].[ProductCostHistory] where [ProductID] = 2;
delete from [Production].[ProductDocument] where [ProductID] = 2;
delete from [Production].[ProductInventory] where [ProductID] = 2;
delete from [Production].[ProductListPriceHistory] where [ProductID] = 2;
delete from [Production].[ProductProductPhoto] where [ProductID] = 2;
delete from [Production].[ProductReview] where [ProductID] = 2;
delete from [Purchasing].[ProductVendor] where [ProductID] = 2;
delete from [Purchasing].[PurchaseOrderDetail] where [ProductID] = 2;
delete from [Sales].[ShoppingCartItem] where [ProductID] = 2;
delete from [Sales].[SpecialOfferProduct] where [ProductID] = 2;
delete from [Production].[TransactionHistory] where [ProductID] = 2;
delete from [Production].[WorkOrder] where [ProductID] = 2;
delete from [Production].[Product] where [ProductID] = 2;