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SQL Server 入門

John MacKintosh

Instructor

超市貨架與購物車

鍵盤與資料庫圖示

SQL Server 與 Transact-SQL

SQL Server－Microsoft 開發的關聯式資料庫系統
Transact-SQL（T-SQL）－Microsoft 的 SQL 實作，並擴充功能
本課程：掌握 T-SQL 基礎
學會撰寫查詢

打開筆電開始學習

查詢入門 101

SQL Server：存放資料庫與資料表的「商店」
查詢：像在不同走道「挑選」商品，放進購物車
SELECT：擷取資料的關鍵詞

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           |
| ...                                 |
+-------------------------------------+

選取多個欄位

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         |
+-----------+----------------------+

查詢格式化

SELECT description, event_year, event_date
FROM grid;

SELECT 
  description, 
  event_year, 
  event_date
FROM 
  grid;

選取 TOP ()

-- 只回傳 5 列
SELECT TOP(5) artist
FROM artists;

-- 回傳前 5% 的列
SELECT TOP(5) PERCENT artist 
FROM artists;

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

選取 DISTINCT

-- 回傳資料表中的所有列
SELECT nerc_region 
FROM grid;

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

-- 回傳不重複的列
SELECT DISTINCT nerc_region 
FROM grid;

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

選取 *

-- 回傳所有列
SELECT * 
FROM grid;

不適合大型資料表

用 AS 更名欄位

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  |
+------------------------------+

來寫些 T-SQL 吧！

SQL Server 入門