﻿ SQL: Employees joining on given days, ascending in seniority

# SQL Exercise: Employees joining on given days, ascending in seniority

## SQL employee Database: Exercise-72 with Solution

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72. From the following table, write a SQL query to find those employees who joined on 1-MAY-91, or 3-DEC-91, or 19-JAN-90. Sort the result-set in ascending order by hire date. Return complete information about the employees.

Pictorial Presentation:

Sample table: employees

Sample Solution:

``````SELECT *
FROM employees
WHERE hire_date IN ('1991-5-01',
'1991-12-03',
'1990-01-19')
ORDER BY hire_date ASC;
``````

Sample Output:

``` emp_id | emp_name | job_name | manager_id | hire_date  | salary  | commission | dep_id
--------+----------+----------+------------+------------+---------+------------+--------
66928 | BLAZE    | MANAGER  |      68319 | 1991-05-01 | 2750.00 |            |   3001
69062 | FRANK    | ANALYST  |      65646 | 1991-12-03 | 3100.00 |            |   2001
69000 | JULIUS   | CLERK    |      66928 | 1991-12-03 | 1050.00 |            |   3001
(3 rows)
```

Explanation:

The said query in SQL that returns all the rows and columns from the 'employees' table where the "hire_date" column matches either '1991-5-01', '1991-12-03', or '1990-01-19', and sorts the result set in ascending order on "hire_date" column.

Relational Algebra Expression:

Relational Algebra Tree:

## Practice Online

Sample Database: employee

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Previous SQL Exercise: Display the location of CLARE.
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## SQL: Tips of the Day

Grouped LIMIT in PostgreSQL: Show the first N rows for each group?

```db=# SELECT * FROM xxx;
id | section_id | name
----+------------+------
1 |          1 | A
2 |          1 | B
3 |          1 | C
4 |          1 | D
5 |          2 | E
6 |          2 | F
7 |          3 | G
8 |          2 | H
(8 rows)
```

I need the first 2 rows (ordered by name) for each section_id, i.e. a result similar to:

```id | section_id | name
----+------------+------
1 |          1 | A
2 |          1 | B
5 |          2 | E
6 |          2 | F
7 |          3 | G
(5 rows)
```

PostgreSQL v9.3 you can do a lateral join

```select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer
join lateral (
select * from t t_inner
where t_inner.section_id = t_outer.section_id
order by t_inner.name
limit 2
) t_top on true
order by t_outer.section_id;
```

Database: PostgreSQL

Ref: https://bit.ly/3AfYwZI

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