Sorteren en filteren

Introductie tot SQL Server

John MacKintosh

Instructor

Order! Order!

Tabellen bestaan uit rijen en kolommen
Queries geven sets of subsets terug

Sets hebben geen vaste volgorde
Is volgorde belangrijk? Gebruik ORDER BY

SELECT TOP (10) prod_id, year_intro 
FROM products 
-- Oplopend sorteren
ORDER BY year_intro, product_id;

+------------+-------------+
| product_id | year_intro  |
|------------+-------------|
| 36         |  1981       |
| 37         |  1982       |
| 38         |  1983       |
| 39         |  1984       |
| 40         |  1984       |
| 41         |  1984       |
| 52         |  1985       |
| 43         |  1986       |
| 44         |  1987       |
| 54         |  1987       |
+------------+-------------+

SELECT TOP (10) product_id, year_intro 
FROM products 
-- year_intro aflopend sorteren
ORDER BY year_intro DESC, product_id;

+------------+-------------+
| product_id | year_intro  |
|------------+-------------|
| 158        |  2015       |
| 173        |  2015       |
| 170        |  2014       |
| 171        |  2014       |
| 172        |  2014       |
| 144        |  2013       |
| 146        |  2013       |
| 147        |  2013       |
| 148        |  2013       |
| 149        |  2013       |
+------------+-------------+

SELECT 
  TOP (10) appearances, 
  year_intro 
FROM products 
-- Sorteren in verschillende richtingen
ORDER BY 
  year_intro DESC, 
  appearances;

+-------------+------------+
| appearances | year_intro |
|-------------+------------|
| 35          | 2015       |
| 74          | 2015       |
| 29          | 2014       |
| 45          | 2014       |
| 48          | 2014       |
| 12          | 2013       |
| 13          | 2013       |
| 14          | 2013       |
| 22          | 2013       |
| 24          | 2013       |
+-------------+------------+

SELECT 
  TOP (10) appearances, 
  year_intro 
FROM products 
-- Beide kolommen aflopend
ORDER BY 
  year_intro DESC, 
  appearances DESC;

+-------------+------------+
| appearances | year_intro |
|-------------+------------|
| 74          | 2015       |
| 35          | 2015       |
| 48          | 2014       |
| 45          | 2014       |
| 29          | 2014       |
| 837         | 2013       |
| 642         | 2013       |
| 561         | 2013       |
| 491         | 2013       |
| 198         | 2013       |
+-------------+------------+

SELECT city_id, name_alias
FROM invoice
-- Tekst sorteren (oplopend)
ORDER BY name_alias;

+-------------+----------------+
| city_id     | name_alias     |
|-------------+----------------|
|  48         | Amsterdam      |
|  59         | Bangalore      |
|  36         | Berlin         |
|  38         | Berlin         |
|  42         | Bordeaux       |
|  23         | Boston         |
|  13         | Brasília       |
|   8         | Brussels       |
|  45         | Budapest       |
|  56         | Buenos Aires   |
+-------------+----------------+

SELECT city_id, name_alias 
FROM invoice
-- Tekst sorteren (aflopend)
ORDER BY name_alias DESC;

+-------------+----------------+
| city_id     | name_alias     |
|-------------+----------------|
|  33         | Yellowknife    |
|  32         | Winnipeg       |
|  49         | Warsaw         |
|   7         | Vienne         |
|  15         | Vancouver      |
|  27         | Tucson         |
|  29         | Toronto        |
|   2         | Stuttgart      |
|  51         | Stockholm      |
|  55         | Sydney         |
+-------------+----------------+

Wat als we alleen rijen willen met bepaalde criteria?

SELECT customer_id, total
FROM invoice 
WHERE total > 15;

Eerste 3 klanten met factuurwaarde > 15

+-------------+------------+
| customer_id | total      |
|-------------+------------|
| 57          | 17.91      |
|  7          | 18.86      |
| 45          | 21.86      |
+-------------+------------+

-- Rijen met punten groter dan 10
WHERE points > 10

-- Rijen met punten kleiner dan 10
WHERE points  < 10

-- Rijen met punten groter dan of gelijk aan 10
WHERE points >= 10

-- Rijen met punten kleiner dan of gelijk aan 20
WHERE points  <= 20

-- Teksttype
WHERE country = 'Spain'

-- Datumtype 
WHERE event_date = '2012-01-02'

SELECT customer_id, total 
FROM invoice 
-- Testen op ongelijkheid
WHERE total <> 10;

+------------+-------+
| customer_id | total |
|------------+-------|
| 2          | 1.98  |
| 4          | 3.96  |
| 8          | 5.94  |
| 14         | 8.91  |
| 23         | 13.86 |
| 37         | 0.99  |
+------------+-------+

Between

SELECT customer_id, total 
FROM invoice 
WHERE total BETWEEN 20 AND 30;

+------------+--------+
| customer_id | total  |
|------------+--------|
| 45         | 21.86  |
| 46         | 21.86  |
| 26         | 23.86  |
| 6          | 25.86  |
+------------+--------+

SELECT customer_id, total 
FROM invoice 
WHERE total NOT BETWEEN 20 AND 30;

+------------+--------+
| customerid | total  |
|------------+--------|
|  2         | 1.98   |
|  4         | 3.96   |
|  8         | 5.94   |
| 14         | 8.91   |
+------------+--------+

Wat is NULL?

NULL betekent: geen waarde voor dat record
NULL’s tonen gaten in onze data

SELECT 
  TOP (6) total, 
  billing_state 
FROM invoice 
WHERE billing_state IS NULL;

+-------+---------------+
| total | billing_state |
|-------+---------------|
| 1.98  | NULL          |
| 3.96  | NULL          |
| 5.94  | NULL          |
| 0.99  | NULL          |
| 1.98  | NULL          |
| 1.98  | NULL          |
+-------+---------------+

SELECT 
  TOP (6) total, 
  billing_state 
FROM invoice 
WHERE billing_state IS NOT NULL;

+--------+---------------+
| total  | billing_state |
|--------+---------------|
|  8.91  | AB            |
| 13.96  | MA            |
|  5.94  | Dublin        |
|  0.99  | CA            |
|  1.98  | WA            |
|  1.98  | CA            |
+-------+----------------+

Laten we sorteren!

Introductie tot SQL Server