Updating primary key sql C2c random chat without registration
If a table already exists, you can add PRIMARY KEY constraint, provided that no other PRIMARY KEY constraint already exists. If a PRIMARY KEY constraint already exists, you can modify or delete it.For example, you may want the PRIMARY KEY constraint of the table to reference other columns, or you may want to change the column order, index name, clustered option, or fill factor of the PRIMARY KEY constraint.Because anyway the check is done at the end of DML or Transaction. I would appreciate if you could give us an example. you just demonstrated that the documentation is accurate: ...Restrictions: You cannot defer a NOT DEFERRABLE constraint with the SET CONSTRAINT(S) statement. Hi Tom, If we create constraints on EMP and DEPT (Both INITIALLY DEFERRED) or If we create RI constraint on EMP (INITIALLY DEFERRED) then directly we can update the master (DEPT) and child (EMP). do you recommend to make all primary key/foreign key constraints deferred when I create them? If I did not do that, and decided to defer it after creation can I do something like "Alter table emp set constraint xxx deferred".MU =================================================== that won't work until we defer the constraints: set constraints all deferred; It makes it so that any constraint that is deferrable (to be checked at COMMIT, not at the statement level) is in fact deferred. Most people would defer the constraint when needed -- especially since a primary key should never in a billion years be updated.
when you wanted to verify that your update is commitable (eg: in your example, you could use set constraints to test the constraints to see if the commit will succeed or fail) October 26, 2002 - am UTC try the commands yourself. Or search for "set constraints" (with quotes) for other threads where this has been discussed. Tom: well as you know judgements keep changing as system requirements keep developing. anyway it seems to that you always should defer a foreign key constraint when you need to update parent table.im in floor #2 ,my room is 205 and I mistook it for room 215, since both rooms are on floor #2 i could choose either, but that doesnt mean its my room)...should i leave the composite key still and update cascade, or create a unique conrtaint on that composite key and add a surrogate key as PK...thanks?You can create a single PRIMARY KEY constraint as part of the table definition when a table is created.Restrictions: You cannot defer a NOT DEFERRABLE constraint with the SET CONSTRAINT(S) statement.You cannot specify either DEFERRABLE or NOT DEFERRABLE if you are modifying an existing constraint directly (that is, by specifying the ALTER TABLE ... You cannot alter a constraint's deferrability status. If the constraint is either "INITIALLY IMMEDIATE" or "INITIALLY DEFERRED" then what is the need to use the SET CONSTRAINTS clause. October 24, 2002 - am UTC an example of what exactly???