You can specify type constraints like this : class StackPanel<TBase extends SomeType> extends Panel<TBase> { } The language specification says : A type parameter T may be suffixed with an extends clause that specifies the upper bound for T. If no extends clause is present, the upper bound is Object. It is a static type … Read more
When you create the table you can do something of this sort, CREATE TABLE names ( name text CONSTRAINT namechk CHECK (char_length(name) <= 255) ) (namechk is just a name for the constraint) Same goes for ALTER TABLE for example: ALTER TABLE names ADD CONSTRAINT namechk CHECK (char_length(name) <= 255);
To find the name of the unique constraint, run SELECT conname FROM pg_constraint WHERE conrelid = ‘cart’::regclass AND contype=”u”; Then drop the constraint as follows: ALTER TABLE cart DROP CONSTRAINT cart_shop_user_id_key; Replace cart_shop_user_id_key with whatever you got from the first query.
EXEC sp_MSforeachtable @command1=”ALTER TABLE ? NOCHECK CONSTRAINT ALL” GO You may also want to do this: EXEC sp_MSforeachtable @command1=”ALTER TABLE ? DISABLE TRIGGER ALL” GO To enable them afterwards EXEC sp_MSforeachtable @command1=”ALTER TABLE ? ENABLE TRIGGER ALL” GO — SQL enable all constraints – enable all constraints sql server — sp_MSforeachtable is an undocumented system … Read more
Use a check constraint: CREATE TABLE foobar( x TEXT NOT NULL UNIQUE, CHECK (x <> ”) ); INSERT INTO foobar(x) VALUES(”);
This is perfectly fine for CONSTRAINT CHECK. Just do this: Requirement: is it possible to create a constraint such that a column B can be null as long column A contains lets say ‘NEW’ but if the contents of column A changes to something else then column B is no longer allowed to be null? … Read more
Use the information_schema.table_constraints table to get the names of the constraints defined on each table: select * from information_schema.table_constraints where constraint_schema=”YOUR_DB” Use the information_schema.key_column_usage table to get the fields in each one of those constraints: select * from information_schema.key_column_usage where constraint_schema=”YOUR_DB” If instead you are talking about foreign key constraints, use information_schema.referential_constraints: select * from … Read more
This typically is unwarranted in C++, as other answers here have noted. In C++ we tend to define generic types based on other constraints other than “inherits from this class”. If you really wanted to do that, it’s quite easy to do in C++11 and <type_traits>: #include <type_traits> template<typename T> class observable_list { static_assert(std::is_base_of<list, T>::value, … Read more
drop constraint and recreate it alter table Persion drop CONSTRAINT <constraint_name> alter table Persion add primary key (persionId,Pname,PMID) edit: you can find the constraint name by using the query below: select OBJECT_NAME(OBJECT_ID) AS NameofConstraint FROM sys.objects where OBJECT_NAME(parent_object_id)=’Persion’ and type_desc LIKE ‘%CONSTRAINT’