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PostgreSQL Alter Table: Alter a table to drop the existing foreign key referenced by the primary key of another table


11. Write a SQL statement to drop the existing foreign key fk_job_id from job_history table on job_id column, which is referenced to the job_id of jobs table

Here is the structure of the table job_history.

postgres=# \d job_history

    Column     |         Type          | Modifiers
---------------+-----------------------+-----------
 employee_id   | numeric(6,0)          |
 start_date    | date                  |
 end_date      | date                  |
 job_id        | character varying(10) |
 department_id | numeric(4,0)          |
Foreign-key constraints:
    "fk_job_id" FOREIGN KEY (job_id) REFERENCES jobs(job_id) ON UPDATE RESTRICT ON DELETE CASCADE

Now execute the following statement.

Sample Solution:

Code:

ALTER TABLE job_history
DROP CONSTRAINT fk_job_id;

Output:

Now see the structure of the table job_history after being altered.

postgres=# \d job_history
 
    Column     |         Type          | Modifiers
---------------+-----------------------+-----------
 employee_id   | numeric(6,0)          |
 start_date    | date                  |
 end_date      | date                  |
 job_id        | character varying(10) |
 department_id | numeric(4,0)          |

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Previous: Write a SQL statement to add a foreign key constraint named fk_job_id on job_id column of job_history table referencing to the primary key job_id of jobs table.
Next: Write a SQL statement to add an index named index_job_id on job_id column in the table job_history.

What is the difficulty level of this exercise?



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