choose two
Which two statenents are tue about the COUNT function?
A) It can only be used for NUMBER data types.
B) COUNT (DISTINCT inv_amt) returns the number of rows excluding rows containing dupicates and NULLs in the INV_AMT column
C) COUNT(*) returns the number of rows in a table including duplicate rows and rows containing NULLs in any column.
D) A SELECT statement using the COUNT function with a DISTINCT keyword cannot have a WHERE clause.
E) COUNT(inv_amt) returns the number of rows in a table including rows with NULL in the INV_AMT column.
Answer::BC
(解析:count 对于 null 值是忽略的;可以与 where 一起使用。)
原创声明:本文系作者授权腾讯云开发者社区发表,未经许可,不得转载。
如有侵权,请联系 cloudcommunity@tencent.com 删除。
原创声明:本文系作者授权腾讯云开发者社区发表,未经许可,不得转载。
如有侵权,请联系 cloudcommunity@tencent.com 删除。