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Can you have a unique constraint on a NULLable column?
A primary key is not allowed on NULLable columns. Both a unique constraint (which creates an index beneath the covers) and an explicitly created unique index are allowed on NULLable columns, and enforce their uniqueness in T-SQL using the aforementioned logic.
Are soft deletes bad?
One of the major problem for soft delete is those unwanted data will potentially affects the db performance. Several years ago one of my Client requested me to do soft delete on all database items, my solution to that is to move all “deleted” items to a backup table, instead of leaving it to the current running tables.
Does soft delete need?
Soft deletion is a widely used pattern applied for business applications. It allows you to mark some records as deleted without actual erasure from the database. Effectively, you prevent a soft-deleted record from being selected, meanwhile, all old records can still refer to it.
Which of the following are benefits of using soft deletes to remove rows from your application?
The advantage of soft-delete concept is, as you never physically delete the data, there is no risk of loss of data when something goes wrong (with the delete action, not with your code). It’s easy to get back the record by just changing the flag.
Can nullable fields be unique?
Multiple NULL values can coexist in a column defined UNIQUE . The manual: In general, a unique constraint is violated when there is more than one row in the table where the values of all of the columns included in the constraint are equal.
What does soft delete mean?
To mark a record in a database for deletion or to temporarily prevent it from being selected.
What is soft delete in laravel?
How Soft Delete works In Laravel. When models are soft deleted, they are not actually removed from your database. Instead, a timestamp is set on the deleted_at column. If a model has a non-null deleted_at value, the model has been soft deleted.
What means soft deleted?
How do you perform a soft delete?
Normally when you run a DELETE statement in a database, the data’s gone. With the soft delete design pattern, you add a bit column like IsDeleted, IsActive, or IsArchived to the table, and instead of deleting rows, you flip the bit column.
What is hard delete and soft delete?
Soft deletes resolves this: the data still exists in the database, and it is possible to clear the deleted flag. Soft deletes: marking data as deleted. Hard deletes: performing a DELETE on a table.
How to create unique constraint that also allows nulls?
If your column is numeric, there may be the challenge of ensuring that the unique constraint using Coalesce does not result in collisions. In that case, there are some options. One might be to use a negative number, to put the “surrogate NULLs” only in the negative range, and the “real values” only in the positive range.
How to create unique constraint in SQL Server?
In SQL Server 2008, you can define a unique filtered index based on a predicate that excludes NULLs: In earlier versions, you can resort to VIEWS with a NOT NULL predicate to enforce the constraint. For SQL Server 2005 and earlier, you can do it without a view.
How to create unique but nullable Index in SQL Server?
For people who are using Microsoft SQL Server Manager and want to create a Unique but Nullable index you can create your unique index as you normally would then in your Index Properties for your new index, select “Filter” from the left hand panel, then enter your filter (which is your where clause). It should read something like this: