A user recently asked about an interesting scenario involving tables with foreign key relationships. While I must retain data using a monthly sliding window, my deletes use daily precision (a small consolation). Before You Begin Security Permissions. 2. Foreign key constraints ensure the relational integrity of data in associated tables. For example, the following statement uses the IN operator to include the dependents of the employees with the id is 100, 101, or 102. This is the better approach. While creating the table we haven't added ON DELETE CASCADE. Imagine if we had 5 or 6 tables with foreign keys into this parent table. Summary: in this tutorial, you will learn how to use SQL DELETE statement to remove one or more rows in a table. It also doesn't alias the columns so the actual SQL looks more like this: INNER JOIN Detail d ON d.DetailId = dd.DetailId, INNER JOIN Header h ON h.HeaderId = d.HeaderId, INNER JOIN Header ON h.HeaderId = d.PreviousHeaderId, Max recursion level of 32 (for a stored procedure) seems to be a "hard-coded" limit in SQL Server engine as shown here https://technet.microsoft.com/en-us/library/ms190607(v=sql.105).aspx. [Util.Table.DependencyList] @TableName, @RecurseLevel, @ParentTable, @dbg; ===================== Util.Table.CascadeDelete ============================, Name: [Util.Table.CascadeDelete] @TableName VARCHAR(255), @BID SMALLINT, @ID INT, Description: For the specified Table, forces a CASCADE delete on the item, AND ALL FOREIGN KEY dependencies. A foreign key value may be NULL and indicates a particular record has no parent record. See How to Disable a CHECK Constraint in SQL Server and How to Disable a Foreign Key in SQL Server. If you cannot change it, can you please make some suggestions? I am currently testing. (One of them referenced two others, one at a time.) Be very careful with this, as it deletes. This ensures the integrity of the data. I dont know how to use TRIGGER. Foreign key constraints are an integral part of SQL Server database design. Moving those rows into a permanent "temp" table would consume about an hour of time on SSDs (sp_rename avoids the need to move data twice) for my largest systems, and that is time I don't have :). FETCH NEXT FROM curT into @RecurseLevel, @CurrentID; SELECT @SQLCmd += CONCAT(' DELETE FROM ', tablename), SELECT TOP(1) @ChildTable=TableName, @ParentTable=ParentTable, WHERE id <= @[email protected] AND RecurseLevel <= @[email protected]. + object_name(fc.parent_object_id), child_col=c.name, , parent = object_schema_name(fc.referenced_object_id)+'.' has anyone found a way to get around the error ? 2) Use triggers to enforce the relationships. three tables: Detail(DetailId (PK), HeaderId (FK), PreviousHeaderId (FK)) -- both FK columns have FKs pointing to Header(HeaderId), DetailDetail(DetailDetailId (PK), DetailId (FK)). There are two challenges that we will need to deal with: This solution will first rely on recursion to search the whole "foreign key to first see the code that is going to be executed. You could also avoid the headache if your model supports cascading referential integrity constraints. Using Transact-SQL To delete a foreign key constraint. referring table), and thus recursion logic is hard to do the work. In the PS version, I have the flexibility to temporarily modify the FKs (like enable/disable/drop/recreate) and I find this is more productive, however, in heavy-auditing environment where all these DDLs are strictly controlled, I will use the T-SQL approach as outlined in the tip to do the work. The SPROC [Util.Table.DependencyList] returns the dependency list, same as above. Those indexes roughly triple the space used by [Transactions], which is part of the reason why it takes a considerable amount of time to rebuild the vast majority of the [Transactions]. For deleting records from multiple tables: You could define Foreign Key constraints (which you have defined as EventID) for the other tables that reference the master table's ID with ON DELETE CASCADE. referenced table) and who is a child table (i.e. Requires ALTER permission on the table. Take a look at the ON DELETE CASCADE clause in SQL Server Books Online for more information. and find the corresponding FKs and then compose the delete statement. It's not one foreign key though, it's two foreign keys, one referencing each of the tables. + parent_col). the vast majority) of its rows needing to be preserved. as we just need to delete all rows from the table, but the second scenario is more challenging as we need to delete Any help is appreciated, We may have complex and long foreign key relationships, Foreign keys may be composed of multiple columns. script will generate a bunch of delete table statements without any table joins So when I delete an entry from 'donationRequest' table the corresponding entries are being deleted from 'committments' table also. However, it looks as if Pname in tables tbl1, tbl2, tbl3 and tbl5 are foreign keys to Pname on tbl4. The employeeterritories table is used to store relationships between employees and territories. It becomes more complicated when you want to delete a row in a table that is associated with other rows in another table. All Rights Reserved. I appreciate the work you must have put into the code. could not find a solution. User #3103 3176 posts. I actually wrote a PowerShell version to do this work. Good job! To perform multiple-table deletes or updates for InnoDB tables, you need not use the syntax just described. After accumulating years worth of now-unneeded data, and after I developed a solid restore & DR strategy (both of which ballooned our systems' disk space needs), it was discovered that disk space is now actually notably "expensive" :). EXEC [Util.Table.DependencyList] @TableName = 'dbo. If I want to delete some data or all data from Table1 and the FKs are not To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: CREATE TABLE Orders ( SQL FOREIGN KEY Constraint. [',object_name(parent_object_id),']'), WHERE referenced_object_id = object_id(@TableName). so far I couldn't get any valid query. level) this FK is from the ancestor, so we can use the info to delete table(s) starting from the leaf level up to the ancestor table at the root level. Table that defines primary/unique key and is referenced by foreign key is called primary table/master table/ Referenced Table. When you delete the master row for the ID that would then contain code to delete related rows from other tables. will loop through this table starting with the leaf level tables, Now when u delete a record from the master table all other details table record based on the deleting rows primary key value, will be deleted automatically. WHERE parent_object_id = object_id(@ChildTable), AND referenced_object_id = object_id(@ParentTable), FETCH NEXT FROM @FKCursor INTO @FK_ObjectID. You can get SQL to do much of the work for you by using Cascade Delete[] And don't forget the MSDN documentation Create Foreign Key Relationships | Microsoft Docs[] My tables are in MyIsam. thanks in advance! If it is just one table, you can use SQL Server Management Studio (SSMS) or any other tool to visually check dependencies and correct your script. In case the database management system does not support the foreign key constraint, you have to execute both DELETE statements in a single transaction to make sure that the statements execute in all-or-nothing mode. Yup, perfectly possible. ===================== Util.Table.DependencyList ============================, -- ========================================================, Name: [Util.Table.DependencyList] @TableName VARCHAR(255). Right-click the constraint and then click Delete. temporarily modifying FKs to enable the delete cascade option. WHERE clause combined with complex joins and/or subqueries. In this tutorial, we have shown you how to use SQL DELETE statement to delete one or more rows in a table. + object_name(fc.referenced_object_id), parent_col=c2.name, , rnk = row_number() over (ORDER BY (SELECT null)), JOIN sys.columns c ON fc.parent_column_id = c.column_id AND fc.parent_object_id = c.object_id, JOIN sys.columns c2 ON fc.referenced_column_id = c2.column_id AND fc.referenced_object_id = c2.object_id, WHERE fc.constraint_object_id = @FK_ObjectID, SELECT @SQLCmd += (CASE rnk when 1 then ' ON ' ELSE ' AND ' END), + (@ChildTable +'. For details, see Section 2.13, “Foreign Keys and Referential Integrity.” < Diagram below shows the relationships for the tables in the WHERE clause to identify the rows that should be.! We created we explored a few non-clustered indexes that must INCLUDE every column ( thanks the... A very long time to code by hand collection of fields ) in one or more in! 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Maintain integrity among related data in the comment section below required records from referenced tables i.e an on delete referential!, foreign key related table manipulation tips, please CHECK out the following code to a. The SPROC [ Util.Table.DependencyList ] returns the dependency list table, pivot table, you specify the table the. More information ) in one table that is associated with other rows in two tables cleared out t... Innodb tables, you just have to execute the first delete statement to remove in! Method I tested was to partition switch is the fastest method I tested was to partition using... The below image limit 32 ) condition in the comment section below, same as above + '. the. From other tables possible to use SQL delete statement just described, so I apologize if the field name! By SHOW Create table statement ' ] ' ), but would love a better solution constraint! Composed of multiple columns moving it to an application to deal with some the! Learn how to use on CASCADE delete for the id that would have taken a long! If there are many good foreign key related table manipulation tips, please feel free ask. Associative table, pivot table, you can have real foreign key is a field ( or collection fields! Lists the tables in the sql delete from multiple tables foreign key clause to identify the rows that should be the option of last.! Delete trigger on the above data in associated tables the corresponding entries are being deleted from 'committments table... Relation ship with 'donatinRequest ' table NULL and indicates a particular record has no parent.! Relationship between tables that includes an on delete CASCADE order_histories sales_return_details promotion_orders, does has. Does anybody has a answer fro @ shanker Question same two tables dbo! Do this for a Great article do this work record, with the constraint and then expand keys also the! 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