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COUNT

COUNT is a SQL function that returns the number of rows that match a specified criteria. Essentially, COUNT function is used when you need to know the count of a record in a certain table's column.

There are two types of count function; COUNT(*) and COUNT(column).

  • COUNT(*) counts all the rows in the target table whether columns contain null values or not.
SELECT COUNT(*) FROM table_name;
  • COUNT(column) counts the rows in the column of a table excluding null.
SELECT COUNT(column_name) FROM table_name;

You may also use COUNT() in conjunction with GROUP BY to return the count of rows within each group.

A typical example would be:

SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;

Here, column_name is the name of the column based on which the rows will be grouped. This query will return the count of rows in each group of column_name.

By understanding how to use the COUNT() function, you can extract more meaningful data from your tables, and perform analytics and generate reports based on the counts of certain attributes in your database.