You can define referential integrity constraints at the column level or the table level. The referential integrity constraints in the preceding examples were defined at the column level, using the references keyword in the create table statement.
When you define table-level referential integrity constraints, include the foreign key clause and a list of one or more column names. foreign key specifies that the listed columns in the current table are foreign keys whose target keys are the columns listed the following references clause. For example:
constraint sales_detail_constr foreign key (stor_id, ord_num) references my_salesdetail(stor_id, ord_num)
The foreign key syntax is permitted only for table-level constraints, and not for column-level constraints. For more information, see “Specifying table-level or column-level constraints”.
After defining referential integrity constraints at the column level or the table level, you can use sp_primarykey, sp_foreignkey, and sp_commonkey to define the keys in the syskeys system table.
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