Usage of the count function in Oracle

Usage of the count function in Oracle

Count is used to count the number of records in the query results.

Example Table t_test

Name	Gender	Age	Salary
Zhang San	Male	23	2000
Li Si	Female	34
Wang Wu	Male	25	1300

 

 

① Simple application

Query: Select count (*) from t_test;

Result: 3

Explanation: The above query will return the number of records in the t_test table.

② Applications with where conditions

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

Result: 2

Explanation: The above query will return the number of records with the gender field "male" in Table t_test.

③ Application of counting a field

Query: Select count (salary) from t_test

Result: 2

Explanation: The above query will return the number of records in the salary column in The t_test table. If the salary of a record is blank, the result is not counted.

④ Application with distinct

Query: Select count (distint gender) from t_test

Result: 2

Explanation: The preceding query returns the number of records of selectdistinct gender from t_test results.