Check out example codes for "sql count". It will help you in understanding the concepts better.

Code Example 1

/*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;

Code Example 2

SELECT COUNT(column_name)

FROM table_name

WHERE condition;

Code Example 3

SELECT SUM(column_name)
FROM table_name
WHERE condition;

Code Example 4

SELECT COUNT(*)
FROM dbo.bigTransactionHistory;

Code Example 5

/* COUNT() is a function that takes on the name of a clomn as an argument
and counts the number of rows where the column is not null */

SELECT COUNT(column_name)
FROM table_name;

Code Example 6

SELECT AVG(column_name)

FROM table_name

WHERE condition;

Learn ReactJs, React Native from akashmittal.com