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資料庫SQL 基本觀念

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資料庫SQL 基本觀念

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ON DELETE
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Youna's article on MySQL's ON DELETE concept provides a clear understanding of its applications and implications in database management. Explaining ON DELETE SET NULL and ON DELETE CASCADE with practical examples involving tables like 'branch' and 'works_with,' the article is a valuable resource for readers seeking to grasp MySQL's ON DELETE functionality. The SQL queries demonstrate the impact of deleting an employee ('小綠') on the 'branch' and 'works_with' tables, and visual representations through SELECT queries enhance clarity. While the article is informative, the inclusion of specific before-and-after examples could further illustrate the ON DELETE actions. Check out this link for a more in-depth understanding: [IQRA Technology - SQL Training](https://iqratechnology.com/academy/sql-training/sql-database/). Kudos to Youna for presenting this insightful piece.
JOIN 連接 : 可以將2個表格連接在一起
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萬用字元wildcard % 代表多個字元 _代表1個字元
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聚合函數 aggregate function
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這個章節是由MySQL 基本語法 (六)延伸的練習題
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依照上圖的資料表創建出公司的資料庫 Employee CREATE TABLE `employee`( `emp_id` INT PRIMARY KEY, `name` VARCHAR(20), `birth_date` DATE, `sex`VARCHAR(1), `salary
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UPDATE & DELETE : 修改刪除資料
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