﻿ SQL: List the nurses who are yet to be registered

# SQL Exercise: List the nurses who are yet to be registered

## SQL hospital Database: Exercise-1 with Solution

1. From the following table, write a SQL query to find out which nurses have not yet been registered. Return all the fields of nurse table.

Sample table: nurse

Sample Solution:

``````SELECT *
FROM nurse
WHERE registered='false';
``````

Sample Output:

```  employeeid |     name     | position | registered |    ssn
------------+--------------+----------+------------+-----------
103 | Paul Flowers | Nurse    | f          | 333333330
(1 row)
```

Explanation:

The given query in SQL that retrieves all rows from the nurse table where the value of the registered column is 'false'.

The WHERE clause filters the results and returns only the rows where the value of the registered column is 'false'.

Pictorial presentation:

Relational Algebra Expression:

Relational Algebra Tree:

## Practice Online

E R Diagram of Hospital Database:

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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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