What function is the same as the count function in Oracle?

The COUNT function in Oracle is equivalent to the COUNT() function in SQL. It is used to count the number of non-null values ​​in a specified column or expression, including: COUNT(*): Counts the number of all non-null values ​​in the table. COUNT(column_name): Count the number of non-null values ​​in the specified column. COUNT(DISTINCT column_name): Counts the number of unique non-null values ​​in the specified column.

What function in Oracle is the COUNT function equivalent to in SQL?

In Oracle, the COUNT function is the same as the COUNT() function in SQL.

Detailed description

The COUNT function is used to count the number of non-null values ​​in a specified column or expression. It can receive one or more parameters:

• COUNT(*): Counts the number of all non-null values ​​in the table, including empty strings and NULL values.
• COUNT(column_name): Count the number of non-null values ​​in the specified column.
• COUNT(DISTINCT column_name): Count the number of unique non-null values ​​in the specified column.

For example:

SELECT COUNT(*) FROM employees;  -- 计算员工表中所有非空值的个数

SELECT COUNT(salary) FROM employees;  -- 计算员工表中非空工资值的个数

SELECT COUNT(DISTINCT department_id) FROM employees;  -- 计算员工表中唯一部门 ID 的个数

In general, the COUNT function is equivalent to the COUNT() function in SQL and is used to count the number of non-null values ​​in a specific data set or column. number.

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