How to Handle Nested Bulk Inserts with Foreign Key Constraints?

One challenge with nested batch inserts is the insertion order. Suppose you create parent and child tables using foreign key references between them. A parent record usually needs to exist before a child record can be inserted. To handle this issue, the parent record must be inserted first, and then the child record.

The problem is that you cannot insert a child record until the parent record ID is available. One way to overcome this problem is to use a stored procedure to insert records. A stored procedure can insert parent records first and then insert child records. This approach ensures that parent records are inserted before child records and that each child record has a valid parent ID.

Another way to perform nested bulk inserts is to use a technique called "table staging". Table staging involves creating temporary tables to store sub-records. The parent record is inserted first, then the child records are inserted into the temporary table. Once all child records have been inserted, you can use a merge statement to insert the child records into the actual child table. The advantage of this approach is that it ensures that the child records are valid since they are checked against the parent table before inserting.

Finally, you can use the OUTPUT clause in your insert statement to capture and use the primary key (e.g. scope_identity()). This will enable you to loop through child entities. Here's an example of this approach:

<code>            using (var scope = tran.Connection.BeginTransaction())
            {
                using (connectionString.WithTransaction(tran))
                {
                    int scope_identity = 0;
                    foreach (var entity in dataload.Entities){
                        scope_identity = connectionString.ExecuteScalar<int>(
                            $"INSERT INTO tbl_owner(OwnerName) OUTPUT INSERTED.OwnerID Values(@Name)", entity);

                        foreach(var project in entity.Related)
                        {
                          connectionString.Execute(
                              $"INSERT INTO tbl_project(Name, OwnerId) Values(@Name, @OwnerId)",
                                new{Name = project.Name, OwnerId = scope_identity });
                        }
                    }
                    scope.Commit();
                }
            }</code>

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