Count function usage in Oracle

Count function usage in Oracle

Count is used to count the results of a query with several records

Example Table T_test

name	Gender	Age	Wages
Tom	Man	23	2000
John doe	Woman	34
Wang Wu	Man	25	1300

① Simple Application

Query: Select COUNT (*) from t_test;

Results: 3

Explanation: The above query returns the number of bars recorded in the table T_test.

Application of ② with where condition

Query: Select COUNT (*) from t_test where gender = ' male '

Results: 2

Explanation: The above query returns the number of records in the table t_test where the Gender field is "male."

③ the application of a field count

Query: Select count (payroll) from T_test

Results: 2

Explanation: The above query returns the number of records in the Payroll column in table T_test, excluding the results when a record's payroll is empty.

Application of ④ coordination distinct

Query: Select count (Distint sex) from t_test

Results: 2

Explanation: The above query returns the number of record bars for the select distinct gender from t_test result.