/SQL/Postgresql can you have null foreign key

Postgresql can you have null foreign key

A foreign key containing null values cannot match the values of a parent 
key, since a parent key by definition can have no null values. However, a
null foreign key value is always valid, regardless of the value of any of
its non-null parts.

Source: ibm.com

Similar codes

0 vote391 views1 answer
How to install sql in anaconda
SQL
0 vote376 views1 answer
Mysql failed to login as root@localhost
SQL
0 vote374 views1 answer
Set engine to innodb
SQL
0 vote421 views2 answers
Mysql insert rows to another database
SQL
0 vote339 views1 answer
Update if else mysql
SQL
0 vote338 views1 answer
Drop all tables in azure sql database
SQL
0 vote365 views1 answer
How to query without duplicate rows in sql
SQL
0 vote369 views1 answer
Count in sql and diff
SQL
0 vote346 views1 answer
We are intrested to work with your organization
SQL
0 vote348 views1 answer
Sql select with apostrohpe
SQL