Count in SQL

count(*)
--------
select count(*)  from tablename ---- It will return total number of rows in the table

count(1)
--------
select count(1) from tablename    ---- It's also return total number of row in the table

count(column name)
--------------------
select count(columnname) from tablename  ---- It will return total number number of rows
                                                                                   with  data(without null) in that column

Example:
----------
create table tablecount(stdname varchar(50))
insert into tablecount values ('abi')
insert into tablecount values ('paranthaman')
insert into tablecount values (null)             -----this row inserted null values

select count(*) from tablecount
output-->  3

select count(1) from tablecount
output--> 3

select count(stdname) from tablecount
output--> 2