國家安全情報人員考試五等考試-資訊組計算機大意114 年第 30 題單選題考點：WHERE條件判斷考點：SELECT*欄位完整性
假設有一個關聯表格 PRODUCT 如下：
Model number | Product name | Product price | unit
1111 | File cabinet | 150 | 10
1112 | Chair | 290 | 15
1113 | Desk | 250 | 25
1114 | Table | 390 | 30
1115 | Sofa | 490 | 20
請問執行下列的指令會得到什麼結果？
select *
from PRODUCT
where unit < 22
AModel number | Product name | Product price | unit
1111 | File cabinet | 150 | 10
1112 | Chair | 290 | 15
1113 | Desk | 250 | 25
1115 | Sofa | 490 | 20
BModel number | Product name | unit
1111 | File cabinet | 10
1112 | Chair | 15
1113 | Desk | 25
1114 | Table | 30
1115 | Sofa | 20
CModel number | Product name | unit
1111 | File cabinet | 10
1112 | Chair | 15
1115 | Sofa | 20
DModel number | Product name | Product price | unit
1111 | File cabinet | 150 | 10
1112 | Chair | 290 | 15
1115 | Sofa | 490 | 20正確答案
D正確答案
SELECT * 取全部欄位，WHERE unit < 22 篩選unit小於22的列，結果保留1111(10)、1112(15)、1115(20)三筆，答案為D
逐選項解析
AModel number | Product name | Product price | unit
1111 | File cabinet | 150 | 10
1112 | Chair | 290 | 15
1113 | Desk | 250 | 25
1115 | Sofa | 490 | 20WHERE條件判斷✕ 易錯陷阱
包含了unit=25的Desk(1113)，但25不小於22，故此列不應出現；WHERE條件篩選有誤
BModel number | Product name | unit
1111 | File cabinet | 10
1112 | Chair | 15
1113 | Desk | 25
1114 | Table | 30
1115 | Sofa | 20SELECT*欄位完整性✕ 易錯陷阱
缺少Product price欄位，且包含全部5筆資料未做WHERE篩選，SELECT *應回傳所有欄位
CModel number | Product name | unit
1111 | File cabinet | 10
1112 | Chair | 15
1115 | Sofa | 20✕ 易錯陷阱
DModel number | Product name | Product price | unit
1111 | File cabinet | 150 | 10
1112 | Chair | 290 | 15
1115 | Sofa | 490 | 20✓ 正確
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