108.Which two statements are true regarding the COUNT function? (Choose two.)

最新推荐文章于 2023-08-14 22:06:34 发布

今年我18

最新推荐文章于 2023-08-14 22:06:34 发布

阅读量2.5k

点赞数

CC 4.0 BY-SA版权

分类专栏： 1z0-051 文章标签： 1z0-051

本文链接：https://blog.youkuaiyun.com/dwj19830118/article/details/50817726

1z0-051 专栏收录该内容

175 篇文章

订阅专栏

本文详细解析了SQL中COUNT函数的不同用法及其返回结果的特点，包括COUNT(*)、COUNT(字段名)和COUNT(DISTINCT 字段名)的区别，并给出了具体的应用场景。

108.Which two statements are true regarding the COUNT function? (Choose two.)
A.The COUNT function can be used only for CHAR, VARCHAR2, and NUMBER data types.
B.COUNT(*) returns the number of rows including duplicate rows and rows containing NULL value in any of the columns.
C.COUNT(cust_id) returns the number of rows including rows with duplicate customer IDs and NULL value in the CUST_ID column.
D.COUNT(DISTINCT inv_amt)returns the number of rows excluding rows containing duplicates and NULL values in the INV_AMT column.
E.A SELECT statement using the COUNT function with a DISTINCT keyword cannot have a WHERE clause.
答案：BD
解析：count 可以用于任意的类型，count(*) 返回符合条件的所有的行数，count(字段名)返回符合条件的所有的
排除null值得行数，count(distinct 字段名）返回符合条件的排除null值和滤重后的行数