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if you want composite key for using the sql use the following sql query:
select distinct(col_name) from table_name where col_name is null;
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∙ 12y ago
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Can a foreign key be null?
yes .a foreign key can have null values
Does foreign key alllows null values and duplicate values?
A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.A foreign can have null values and it can have duplicate values.
Have foreign keys null values?
Yes Foreign key can have null value.
Difference between foreign key and composite key?
primary key: primary creates a clustered index on the column and it doesn't allow null values. unique key: unique key creates non clustered index by default.it allows "one null value". foreign key: A foreign key (FK) is a column or combination of columns used to establish and enforce a link between the data in two tables. Fore More information, you can visit this website:http://www.iyogibusiness.com
Is a primary key a unique identifier?
NO, unique identifier allows null values.. so u dont called as primary key... primary key means it doesn't allow null n repeated values.... so we dont call unqiue identifier is a primary key...
Difference between composite and primary key?
There are two types of keys in any database; composite and primary keys. Composite key differs from primary key in that it contains more than one column while primary key is composed of only one field and cannot have a null value.
How do you Avoid missing column values for non primary key columns?
Use Default and Not NULL
What is primery key?
primary key is a column or set of columns (called composite primary key ) that identify the table & make every table unique .value of a primary key can not duplicated & can not be NULL .
What is a number for composite?
The cardinality of composite numbers is Aleph-null.
Does primary key allows null value?
No. A primary key requires a value because it is the field that all other values in the row depend on.
What is key constraints?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
What is primary key constraint?
Primary Key is a Constraint Used to avoid Duplicate entries in database table and you define primary key the column doesn't allow NULL values.
