PostgreSQL Alter Table: Alter a table to drop the existing primary key
8. Write a SQL statement to drop the existing primary from the table locations on a combination of columns location_id and country_id.
Here is the structure of the table locations.
postgres=# \d locations
Column | Type | Modifiers
----------------+-----------------------+-----------
location_id | numeric(4,0) | not null
street_address | character varying(40) |
postal_code | character varying(12) |
city | character varying(30) |
state_province | character varying(25) |
country_id | character varying(2) | not null
Indexes:
"locations_pkey" PRIMARY KEY, btree (location_id, country_id)
Now execute the following statement.
Sample Solution:
Code:
ALTER TABLE locations
DROP CONSTRAINT locations_pkey;
Output:
Now see the structure of the table locations after alteration.
postgres=# \d locations Column | Type | Modifiers ----------------+-----------------------+----------- location_id | numeric(4,0) | not null street_address | character varying(40) | postal_code | character varying(12) | city | character varying(30) | state_province | character varying(25) | country_id | character varying(2) | not null
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Previous: Write a SQL statement to add a primary key for a combination of columns location_id and country_id.
Next: Write a SQL statement to add a foreign key on job_id column of job_history table referencing to the primary key job_id of jobs table.
What is the difficulty level of this exercise?
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