Common aggregate functions in sql

SQL common aggregate functions include: COUNT() Calculate the number of rows SUM() Sum AVG() Find the average MIN() Find the minimum value MAX() Find the maximum value

Commonly used aggregate functions in SQL

The aggregate functions in SQL (Structured Query Language) are used to operate on a set of values ​​and combine them Aggregate into one or more values. The most common aggregate functions include:

• COUNT(): Counts the total number of rows in a set of rows, regardless of whether there are values ​​in those rows.
• SUM(): Add a set of values.
• AVG(): Calculate the average of a set of values.
• MIN(): Returns the minimum value in a group.
• MAX(): Returns the maximum value in a group.

Other commonly used aggregate functions:

• GROUP_CONCAT(): Concatenate a set of strings into one string , separated by the specified delimiter.
• FIRST(): Returns the value of the first row in a group.
• LAST(): Returns the value of the last row in a group.
• STDDEV():Calculate the standard deviation of a set of values.
• VARIANCE(): Calculate the variance of a set of values.

Use aggregate functions:

Aggregation functions are usually used in the GROUP BY clause of the SELECT statement, which groups query results by specified columns. For example, the following query calculates the average sales for each group:

<code>SELECT department_name, AVG(sales)
FROM sales
GROUP BY department_name;</code>

Aggregate functions can also be used in the HAVING clause, which filters groups. For example, the following query returns only departments with average sales greater than 1000:

<code>SELECT department_name, AVG(sales)
FROM sales
GROUP BY department_name
HAVING AVG(sales) > 1000;</code>

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