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Hi, I want to practice queries that require having repeated records. This is not allowed by default since it violates uniqueness constraint. Do I just use an alter table drop unique constraint for this?
Thanks, I am trying to use them to test certain queries, like queries done to delete duplicates. So for this, I need to have duplicates which I can then delete.jedishrfu said:Can’t you build a table without the uniqueness? I’ve done that from time to time. These kinds of tables are slower if large and you need to find stuff. You want to avoid table scans that’s why indexes were created.
WWGD said:Hi, I want to practice queries that require having repeated records. This is not allowed by default since it violates uniqueness constraint. Do I just use an alter table drop unique constraint for this?
Yes, this is just small-scale academic effort; I would not experiment in a production environment. Thanks.QuantumQuest said:If the table you want to have duplicate records in has a unique identification column (some sort of an "ID" thing) then (obviously) there is no problem inserting duplicate records or even more than two times the same record. So, I think that you mean that you don't have something like this and hence the uniqueness constraint issue you talk about. In this case - as far as I know, you need to have permission for an "ALTER TABLE" in order to add an identity column. Then you can utilize one of various methods to get rid of the duplicate records i.e. correlated subquery, using temporary table etc. (for these various methods you may want to take a look here). Needless to say that all the above are for testing purposes on a table that you can really alter without affecting the database schema i.e. not on any sort of database in production phase.
Disabling constraints in SQL server is a process of temporarily deactivating a constraint on a table. Constraints are rules that ensure data integrity and prevent invalid data from being inserted into a table. Disabling constraints allows for easier data manipulation and can be useful when bulk loading data or performing large data updates on a table.
To disable a constraint in SQL server, you can use the ALTER TABLE statement and specify the DISABLE keyword followed by the name of the constraint you want to disable. This will temporarily deactivate the constraint and allow you to make changes to the data in the table. Once you are done, you can enable the constraint again using the ENABLE keyword.
Yes, you can disable multiple constraints at once in SQL server by separating the constraint names with a comma after the DISABLE keyword. This can be useful when you need to disable multiple constraints before making changes to a table.
Disabling constraints in SQL server can pose a potential risk to data integrity if not done carefully. It is important to remember to re-enable the constraints after making changes to the data to ensure that the data remains consistent. Additionally, disabling constraints can also impact the performance of database operations as the server will not be able to enforce the constraints during data manipulation.
Yes, there are alternatives to disabling constraints in SQL server. One alternative is to use the NOCHECK option when inserting or updating data. This will temporarily disable the constraints during the data manipulation and then re-enable them once the operation is complete. Another alternative is to use the WITH (CHECK_CONSTRAINTS = OFF) option when performing a bulk insert or update, which will temporarily disable all constraints on the table until the operation is complete.