标签：ann contain types The ret turn state about clu
choose twoWhich 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。)
标签：ann contain types The ret turn state about clu
原文地址：https://blog.51cto.com/13854012/2453142
