SQL Constraint 1

Which of the following constraint ,ORACLE doesn't supports ?

UNIQUE

NOT NULL

CHECK

PRIMARY KEY

Non of these

A table can have more than one primary key column .

true

false

'CHECK ' constraint checks whether the condition specified in the constraint is satisfied.

true

false

What is an integrity constraint is a rule ?

An integrity constraint is a rule that restricts the values for more columns in a table or a view.

An integrity constraint is a rule that restricts the values for one columns in a view.

An integrity constraint is a rule that restricts the values for one columns in a table.

An integrity constraint is a rule that restricts the values for one or more columns in a table or a view

Which of the following statements are true about composite primary key ?

A composite key is a primary key that consists of more than one column

Oracle will create a composite primary key index on the table to implement and enforce the composite key.

Composite keys are also known as concatenated or aggregate keys.

All the above

Which of the statements are true about primary key ?

Must uniquely identify the row

Cannot have NULL values

Should not change over the time

All the above

CREATE TABLE t1 (c1 NUMBER PRIMARY KEY);

Table t2 has also two column C1 and C2. How to declare C2 as Foreign Key which should point Primary Key of t1

CREATE TABLE t2 (
c1 NUMBER PRIMARY KEY,
c2 NUMBER REFERENCES t1(c1) );

CREATE TABLE t2(
c1 NUMBER,
c2 NUMBER,
CONSTRAINT t1_fk FOREIGN KEY (c1) REFERENCES t1);

CREATE TABLE t2 (
c1 NUMBER,
c2 NUMBER,
CONSTRAINT t1_fk FOREIGN KEY (t1) REFERENCES c1);

CREATE TABLE t2 (
c1 NUMBER PRIMARY KEY,
c2 NUMBER REFERENCES c1(t1)

What is Foreign key with ON DELETE CASCADE ?

If rows are deleted from the parent table, referenced rows will automatically be removed from the child table

If rows are deleted from the child table, referenced rows will automatically be removed from the parent table

If rows are deleted from the parent table, referenced rows will automatically be removed from the child table and vice versa ,

All the above

We cannot disable a primary key or unique key if foreign keys that are enable reference it.

true

false

How to disable all the referenced foreign keys and the primary or unique key ?

We can't disable

ALTER TABLE table_name DISABLE CONSTRAINT constraint_name;

ALTER TABLE tablename modify DISABLE CONSTRAINT constraint_name;

ALTER TABLE tablename CONSTRAINT constraint_name DISABLE;