constraints

I would like to add a BOOLEAN column to a MySQL table which will be named is_default . In this column, only one record can have is_default set to true . How can I add this constraint to my column with mysql? Thanks! UPDATE If it is not a constraint that I should add. How are we dealing with this type of problem on DBs? I think this is not the best way to model the situation of a single default value. Instead, I would leave the IsDefault column out and create a separate table with one row and only the column(s) that make(s) up the primary key of your main table. In this table you place the PK

When a unique constraint is violated, a javax.persistence.RollbackException is thrown. But there could be multiple reasons to throw a RollbackException . How can I find out that a unique constraint was violated? try { repository.save(article); } catch(javax.persistence.RollbackException e) { // how to find out the reason for the rollback exception? } Pascal Thivent How can I find out that a unique constraint was violated? Exception are chained, you have to call getCause() recursively to get the provider specific exception (and maybe go down to the SQLException ) to translate it into something

I have a table called PX_Child that has a foreign key on PX_Parent. I'd like to temporarily disable this FK constraint so that I can truncate PX_Parent. I'm not sure how this goes however. I've tried these commands ALTER TABLE PX_Child NOCHECK CONSTRAINT ALL ALTER TABLE PX_Parent NOCHECK CONSTRAINT ALL (truncate commands) ALTER TABLE PX_Child CHECK CONSTRAINT ALL ALTER TABLE PX_Parent CHECK CONSTRAINT ALL But the truncate still tells me it can't truncate PX_Parent because of a foreign key constraint. I've looked all around the net and can't seem to find what I'm doing wrong, sorry for the

I have the following table: CREATE TABLE child( id INTEGER PRIMARY KEY, parent_id INTEGER CONSTRAINT parent_id REFERENCES parent(id), description TEXT); How do I drop the constraint? SQLite does not (as of this answer) support the alter table drop constraint command. The allowed syntax can be seen here . You will need to create a new table without a constraint, transfer the data, then delete the old table. I think something like the following should work: CREATE TABLE child2 ( id INTEGER PRIMARY KEY, parent_id INTEGER, description TEXT ); INSERT INTO child2 (id, parent_id, description) SELECT

My application is localized in both English and Arabic. Unfortunately, sometimes the autolayout behavior for localization is not required. By that, I mean reversing the leading and trailing spaces. I want to override this behavior. Is there any way to do that? To make leading act always as left (and trailing always like right), i.e. make it language independent, you can remove checkmark on "Respect language direction" on all constrains. You can find this checkmark in constrain settings in the Attributes inspector under "First Item" button. The attributes leading and trailing are the same as

I have a Table like this one: |UserId | ContactID | ContactName --------------------------------------- | 12456 | Ax759 | Joe Smith | 12456 | Ax760 | Mary Smith | 12458 | Ax739 | Carl Lewis | 12460 | Ax759 | Chuck Norris | 12460 | Bx759 | Bruce Lee I need to add a constraint to this table so that no user can have duplicate contact id's. The users are importing data from various external systems so ContactId will not be unique across the board but will be unique on a per user basis. I know how to create Unique and Non-Null contraints based on single columns but how can I create a unique