42 cards · basic cards · AI-written, checked twice. Edit anything.
- SELECT 陳述式的基本語法是什麼？
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SELECT column1, column2 FROM table_name- 如何在 SELECT 中用 WHERE 子句篩選資料列？
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SELECT * FROM users WHERE age > 18- ORDER BY 子句的作用是什麼？
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依一個或多個欄位對結果集排序：SELECT * FROM products ORDER BY price DESC- LIMIT 子句的用途是什麼？
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限制回傳的資料列數量：SELECT * FROM orders LIMIT 10- DISTINCT 在 SELECT 中有什麼作用？
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只回傳不重複的值：SELECT DISTINCT country FROM customers- 如何用聚合函式計算資料列數量？
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SELECT COUNT(*) FROM employees- 聚合函式 SUM 的作用是什麼？
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加總欄位中的所有值：SELECT SUM(salary) FROM employees- 如何求出欄位的平均值？
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SELECT AVG(price) FROM items- MAX 函式會回傳什麼？
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欄位中的最大值：SELECT MAX(score) FROM games- MIN 函式會回傳什麼？
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欄位中的最小值：SELECT MIN(salary) FROM employees- GROUP BY 子句的用途是什麼？
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依一個或多個欄位將資料列分組：SELECT department, COUNT(*) FROM employees GROUP BY department- 如何在 GROUP BY 之後篩選分組？
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使用 HAVING：SELECT department, COUNT(*) FROM employees GROUP BY department HAVING COUNT(*) > 5- 什麼是 INNER JOIN？
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回傳兩個資料表中值相符的資料列：SELECT * FROM orders INNER JOIN customers ON orders.customer_id = customers.id- 什麼是 LEFT JOIN？
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回傳左資料表的所有資料列，以及右資料表中相符的資料列：SELECT * FROM customers LEFT JOIN orders ON customers.id = orders.customer_id- 什麼是 RIGHT JOIN？
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回傳右資料表的所有資料列，以及左資料表中相符的資料列：SELECT * FROM orders RIGHT JOIN customers ON orders.customer_id = customers.id
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