Check out example codes for "how to count number of rows in sql". It will help you in understanding the concepts better.

Code Example 1

SELECT COUNT(*)
FROM dbo.bigTransactionHistory;

Code Example 2

/* 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;

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