Adding constraints in sql server comes under which category 开发者_如何转开发DML or DDL?
DDL, as you're defining the relationships between tables, not modifying the data stored in them.
DDL, since they alter the structure rather than the data.
For example: Referential integrity statements
Constraints must be DDL statements.Let's prove it. Create two tables A and B as follows:
create table A ( id int primary key );
create table B ( id int, foreign key id references A(id) );
Now, let's try to insert some data in table A, and then table B.
INSERT into A values (1);
INSERT into B values (1);
Now, try to run TRUNCATE A; It will give Foreign Key Constraint Fail error. It means that Constraints are applied on schema of tables, hence DDL statements.
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