The use of the aggregate function of SQLite

An aggregate function performs a calculation on a set of values and returns a single value. An aggregate function performs a calculation on a set of values and returns a single value. In addition to COUNT, the aggregate function ignores null values. Aggregate functions are often used with the GROUP by clause of a SELECT statement.

COUNT (*)--Returns the number of specified tables

For example: SELECT COUNT (*) from Studen (where ...);

SUM (*)-Returns the sum of data (only works on numeric type fields)

For example:

Returns the sum of the three subjects: select sum (Math) +sum (Chinese) +sum (chinese version) from student;

In summary, an aggregate function is a calculation of the return result of a query, and then returns a value.

The use of the aggregate function of SQLite