Unit 2 · ROUND, CONCAT, UPPER / LOWER

Data file / 資料檔：student table (sql_class) — download and load into sqliteviz.com.

• Unit content + ClassWork 2 / 單元內容及課後練習：sql_class

Start Here / 開始做題

1. Decide whether the task needs a number function (ROUND) or a text function (CONCAT, UPPER, LOWER). 先判斷是數字函式還是文字函式。
2. Wrap only the column that needs changing — leave the others as normal columns. 只對需要處理的欄位套用函式。
3. Always name the new column with AS so the output is easy to read. 使用 AS 為新欄位命名。

Unit Dashboard / 單元地圖

Quick Concepts / 重點

SQL Syntax / SQL 語法

SELECT Name,
       CONCAT(Name, '-', Class) AS name_class,
       ROUND(Grade, 0) AS rounded_grade
FROM student
LIMIT 5;

Yellow Syntax Guide / 黃色語法重點

Dry Run / 手算追蹤

For Name = 'Alice', Class = 'F6A', Grade = 87.6:

Examples / 例題

Example 2-1 · Round a Grade

題目說明 / Problem Statement

Show Name and Grade rounded to 1 decimal place, for the first 5 students. 顯示前 5 位學生的姓名，及四捨五入到小數 1 位的成績。

Reference Answer / 參考答案

SELECT Name, ROUND(Grade, 1) AS rounded_grade
FROM student
LIMIT 5;

Example 2-2 · Combine Name and Class

題目說明 / Problem Statement

Show a single column student_info in the format Alice (F6A), for the first 5 students. 合併姓名與班級成一欄，例如 Alice (F6A)。

Reference Answer / 參考答案

SELECT CONCAT(Name, ' (', Class, ')') AS student_info
FROM student
LIMIT 5;

Example 2-3 · Change Text Case

題目說明 / Problem Statement

Show Name in uppercase and Class in lowercase, for the first 5 students. 把姓名轉換為大寫，班級轉換為小寫。

Reference Answer / 參考答案

SELECT UPPER(Name) AS upper_name, LOWER(Class) AS lower_class
FROM student
LIMIT 5;

ClassWork 2 / 課後練習

Student task / 學生任務：先自行完成 SQL，再用每題下方的截圖核對結果。

Name every calculated column with AS. 每個計算後的欄位都要用 AS 命名。

ClassWork 2-1 · Top 10 by Grade

Show the first 10 students ordered by grade (highest first). 查詢成績最高的前 10 名學生。

Reference Answer / 參考答案

ClassWork 2-2 · Bottom 10 by Grade

Show the last 10 students ordered by grade (lowest first). 查詢成績最低的 10 名學生。

Reference Answer / 參考答案

ClassWork 2-3 · Round All Grades

Round all students' grades to 0 decimal places. Name the column. 把所有學生的成績四捨五入到整數（命名欄位）。

Reference Answer / 參考答案

ClassWork 2-4 · Combine Name and Class

Show student name and class combined as one column in the format: Alice-F6A. Name the column. 把姓名與班級合併成一欄（命名欄位）。

Reference Answer / 參考答案

ClassWork 2-5 · Change Case of Two Columns

Show all student names in uppercase and class in lowercase. Name each column. 將姓名轉大寫、班級轉小寫（命名欄位）。

Reference Answer / 參考答案

Active Recall / 主動回想

• Which function changes a number, and which function joins text?
• Why should a calculated column use AS?
• Predict the output of ROUND(12.56, 1).

Spaced Review / 間隔複習

• Next lesson: create one readable label from a name and class.
• 1 week later: choose between ROUND, CONCAT, UPPER, and LOWER for three new tasks.

Key Takeaways / 重點帶走

• Functions transform a value inside a query.
• AS makes calculated output understandable.
• Transform only the column that needs changing.

Common Mistakes / 常見錯誤

• Forgetting commas between selected columns.
• Giving no AS name to a calculated result.

30-Second Review / 30 秒複習

Say one example use for ROUND, CONCAT, and AS.