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PostgreSQL: Advanced SQL: Foreign keys
- Referential integrity
- Ensures applications/users interact with data in the intended way
- Example: all entries in privileges must have a corresponding entry in 'users
'
01 CREATE TABLE users (
02 usrid int,
03 name text,
04 primary key(usrid));
05
06 CREATE TABLE privileges (
07 usrid int REFERENCES users(usrid),
08 privl int,
09 primary key(usrid));
10
template1=# insert into privileges values(1);
ERROR: insert or update on table "privileges" violates foreign key constraint "$1"
DETAIL: Key (usrid)=(1) is not present in table "users".
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