SQL exercises on employee Database: Display the number of employee for each job in each department
SQL employee Database: Exercise-97 with Solution
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97. From the following table, write a SQL query to count the number of employees of each designation in each department. Return department id, job name and number of employees.
Sample table: employees
SELECT dep_id, job_name, count(*) FROM employees GROUP BY dep_id, job_name;
dep_id | job_name | count --------+-----------+------- 3001 | MANAGER | 1 2001 | ANALYST | 2 3001 | SALESMAN | 4 1001 | MANAGER | 1 1001 | PRESIDENT | 1 2001 | MANAGER | 1 2001 | CLERK | 2 1001 | CLERK | 1 3001 | CLERK | 1 (9 rows)
Relational Algebra Expression:
Relational Algebra Tree:
Sample Database: employee
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Previous: From the following table, write a SQL query to list the managers and number of employees work under them. Sort the result set in ascending order on manager. Return manager ID and number of employees under them.
Next: From the following table, write a SQL query to find those departments where at least two employees work. Return department id, number of employees.
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SQL: Tips of the Day
Delete all Duplicate Rows except for One in MySQL?
SELECT * FROM names; +----+--------+ | id | name | +----+--------+ | 1 | google | | 2 | yahoo | | 3 | msn | | 4 | google | | 5 | google | | 6 | yahoo | +----+--------+
1. If you want to keep the row with the lowest id value:
DELETE n1 FROM names n1, names n2 WHERE n1.id > n2.id AND n1.name = n2.name
2. If you want to keep the row with the highest id value:
DELETE n1 FROM names n1, names n2 WHERE n1.id < n2.id AND n1.name = n2.name
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