Witamy

Wprowadzenie do SQL Server

John MacKintosh

Instructor

SQL Server i Transact-SQL

SQL Server – relacyjny system baz danych firmy Microsoft
Transact-SQL (T-SQL) – implementacja SQL firmy Microsoft z rozszerzoną funkcjonalnością
W tym kursie: opanowanie podstaw T-SQL
Nauka pisania zapytań

Zapytania – podstawy

SQL Server: magazyn zawierający bazy danych i tabele
Zapytania: sposób na wybieranie różnych elementów z różnych działów i umieszczanie ich w koszyku
SELECT: słowo kluczowe do pobierania danych

SELECT description 
FROM grid;

+-------------------------------------+
| description                         |
|-------------------------------------|
| Severe Weather Thunderstorms        |
| Severe Weather Thunderstorms        |
| Severe Weather Thunderstorms        |
| Fuel Supply Emergency Coal          |
| Physical Attack Vandalism           |
| Physical Attack Vandalism           |
| Physical Attack Vandalism           |
| Severe Weather Thunderstorms        |
| Severe Weather Thunderstorms        |
| Suspected Physical Attack           |
| Physical Attack Vandalism           |
| ...                                 |
+-------------------------------------+

Wybieranie więcej niż jednej kolumny

SELECT 
  artist_id, 
  artist_name 
FROM 
  artist;

+-----------+----------------------+
| artist_id | artist_name          |
|-----------+----------------------|
| 1         | AC/DC                |
| 2         | Accept               |
| 3         | Aerosmith            |
| 4         | Alanis Morissette    |
| 5         | Alice In Chains      |
| 6         | Antônio Carlos Jobim |
| 7         | Apocalyptica         |
| 8         | Audioslave           |
| 9         | BackBeat             |
| 10        | Billy Cobham         |
+-----------+----------------------+

Formatowanie zapytań

SELECT description, event_year, event_date
FROM grid;

SELECT 
  description, 
  event_year, 
  event_date
FROM 
  grid;

SELECT TOP ()

-- Return 5 rows
SELECT TOP(5) artist
FROM artists;

-- Return top 5% of rows
SELECT TOP(5) PERCENT artist 
FROM artists;

+-----------------------+
| artist                |
|-----------------------|
| AC/DC                 |
| Accept                |
| Aerosmith             |
| Alanis Morissette     |
| Alice in Chains       |
+-----------------------+

SELECT DISTINCT

-- Return all rows in the table
SELECT nerc_region 
FROM grid;

+-------------+
| nerc_region |
|-------------|
| RFC         |
| RFC         |
| MRO         |
| MRO         |
| ....        |
+-------------+

-- Return unique rows
SELECT DISTINCT nerc_region 
FROM grid;

+-------------+
| nerc_region |
|-------------|
| NPCC        |
| NPCC RFC    |
| RFC         |
| ERCOT       |
| ...         | 
+-------------+

SELECT *

-- Return all rows
SELECT * 
FROM grid;

NIE nadaje się do dużych tabel

Aliasowanie nazw kolumn za pomocą AS

SELECT demand_loss_mw AS lost_demand 
FROM grid;

+-------------+
| lost_demand |
|-------------|
| 424         |
| 217         |
| 494         |
| 338         |
| 3900        |
| 3300        |
+-------------+

SELECT description AS cause_of_outage 
FROM grid;

+------------------------------+
| cause_of_outage              |
|------------------------------|
| Severe Weather Thunderstorms |
| Fuel Supply Emergency Coal   |
| Physical Attack Vandalism    |
| Suspected Physical Attack    |
| Electrical System Islanding  |
+------------------------------+

Napiszmy trochę kodu T-SQL!

Wprowadzenie do SQL Server