如何获取选择语句中第一列的计数

Question

I am trying to replace count (*) with count(column_name)

I am able to get the column_name for some select statements, but few are very complex and I am not able to find what are the columns returned by that select statement.

Is there a way where I can get count(first_column_name) when I am not able to find the column name ?

Answer 1

As told, COUNT(Column_Name) can be replaced by COUNT(n) anytime where n = Position of the column in the dataset.

Eg Suppose there is table MyTable having the below physical structure

EmpID|Name|Location

If you want to get a count of EmpID , use the query

SELECT COUNT(1) FROM MyTable

instead of

SELECT COUNT(EmpID) FROM MyTable

If you want a count of locations, use the query,

SELECT COUNT(3) FROM MyTable

and so on.

For the dataset SELECT Location, EmpID, Name FROM MyTable , to get a count of names, you need to use the query

SELECT COUNT(3) FROM (SELECT Location, EmpID, Name FROM MyTable)A