SQL exercises on employee Database: List the no. of employees and average salary within each department for each job name

SQL employee Database: Exercise-104 with Solution

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104. From the following table, write a SQL query to find number of employees and average salary. Group the result set on department id and job name. Return number of employees, average salary, department ID, and job name.

Sample table: employees

Sample Solution:

SELECT count(*),
       avg(salary),
       dep_id,
       job_name
FROM employees
GROUP BY dep_id,
         job_name;

Sample Output:

 count |          avg          | dep_id | job_name
-------+-----------------------+--------+-----------
     1 | 2750.0000000000000000 |   3001 | MANAGER
     2 | 3100.0000000000000000 |   2001 | ANALYST
     4 | 1500.0000000000000000 |   3001 | SALESMAN
     1 | 2550.0000000000000000 |   1001 | MANAGER
     1 | 6000.0000000000000000 |   1001 | PRESIDENT
     1 | 2957.0000000000000000 |   2001 | MANAGER
     2 | 1050.0000000000000000 |   2001 | CLERK
     1 | 1400.0000000000000000 |   1001 | CLERK
     1 | 1050.0000000000000000 |   3001 | CLERK
(9 rows)

Relational Algebra Expression:

Relational Algebra Tree:

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Sample Database: employee

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Previous: From the following table, write a SQL query to check whether the employees ID are unique or not. Return employee id, number of employees.
Next: From the following table, write a SQL query to find those employees whose name start with 'A' and six characters in length. Return employee name.