what does count do in sql code example

Example 1: sql count

/*COUNT(column_name) will return the number of rows from the column 
that are not NULL*/
SELECT COUNT(column_name)
FROM table_name;

/*COUNT(*) will return the number of rows from the table*/
SELECT COUNT(*)
FROM table_name;

Example 2: sql count(*)

SELECT COUNT(column_name)
FROM table_name
WHERE condition;

Example 3: how to count number of rows in sql

SELECT COUNT(*)
FROM dbo.bigTransactionHistory;