That's all you have to do to create aforeign key in MySQL, but because MySQL supports multiple database engines (database storage engines), you need to know if your foreign key declaration is really going to do what you think it will. MySQL foreign key support in database engines Laughin...
If you do not specify the constraint name when you create aFOREIGN KEYconstraint, the system automatically assigns a constraint name in the format oftable name_OBFK_creation timestamp, such ast1_OBFK_1627747200000000. By default, OceanBase Database checks foreign keys. To disable or enable forei...
Below is an example of specifying the primary key on a single column usingALTER TABLE. The same SQL statement can be used in MySQL, Oracle, and SQL Server. ALTER TABLE Customer ADD PRIMARY KEY (SID); Note: Before using theALTER TABLEcommand to add a primary key, you'll need to make ...
UNIQUE Constraint: Ensures that all values in a column are different.CHECK Constraint: Makes sure that all values in a column satisfy certain criteria.Primary Key Constraint: Used to uniquely identify a row in the table.Foreign Key Constraint: Used to ensure referential integrity of the data....
MySQL tenants of OceanBase Database support theNOT NULL,UNIQUE,PRIMARY KEY,FOREIGN KEY, andCHECKconstraints. NOT NULL ANOT NULLconstraint requires that the constrained column do not contain aNULLvalue. For a column with theNOT NULLconstraint, you must specify the values in theINSERTstatement unless...