SQLBolt：https://sqlbolt.com/lesson/introduction

• SQL Lesson 14: Updating rows
• SQL Lesson 15: Deleting rows

前言

• 資料表（Table）：每一行為唯一資料，每一列為不同屬性。

  這次我們要來修改 & 刪除資料。
  這兩個語法都要需要加上 WHERE 的條件。

SQL Lesson 14: Updating rows

語法

-- Update statement with values
UPDATE mytable
SET column = value_or_expr, 
    other_column = another_value_or_expr, 
    …
WHERE condition;

題目

-- 1. The director for A Bug's Life is incorrect, it was actually directed by John Lasseter
UPDATE movies
SET director = "John Lasseter"
WHERE id = 2;

-- 2. The year that Toy Story 2 was released is incorrect, it was actually released in 1999
UPDATE movies
SET year = 1999
WHERE id = 3;

-- 3. Both the title and director for Toy Story 8 is incorrect! The title should be "Toy Story 3" and it was directed by Lee Unkrich
UPDATE movies
SET title = "Toy Story 3", director = "Lee Unkrich"
WHERE id = 11;

SQL Lesson 15: Deleting rows

語法

-- Delete statement with condition
DELETE FROM mytable
WHERE condition;

題目

-- 1. This database is getting too big, lets remove all movies that were released before 2005.
DELETE FROM movies
where year < 2005;

-- 2. Andrew Stanton has also left the studio, so please remove all movies directed by him.
DELETE FROM movies
where director = "Andrew Stanton";

今天講解完資料操作的部分，明天就要開始介紹如何對資料表進行 新增、修改、刪除 啦。

參考資料：

• SQL Lesson 14: Updating rows
• SQL Lesson 15: Deleting rows
• Day 11 建立資料表 - 修改 ＆ 回傳資料