SQL COUNT()、AVG()和 SUM()

原文:https://www.geeksforgeeks.org/sql-count-avg-and-sum/

  1. SQL COUNT() Function : The COUNT() function provides the number of rows that matches a specified condition.

    COUNT()语法–

    sql SELECT COUNT(column_name) FROM table_name WHERE condition;

  2. SQL AVG() Function : The AVG() function provides the average value of a numeric column.

    AVG()语法–

    ```sql SELECT AVG(column_name) FROM table_name WHERE condition;

    ```

  3. SQL SUM() Function : The SUM() function provides the total sum of a numeric column.

    SUM()语法–

    ```sql SELECT SUM(column_name) FROM table_name WHERE condition;

    ```

我们假设，我们有一个表“GeeksTab”。

名字 城市 薪水 身份证明 (美)司法部(Department of Justice)
字母表 德里 Four thousand five hundred One hundred and thirty-four 8 月 6 日
弥漫性嗜酸细胞增多性筋膜炎 无聊死了 Six thousand five hundred Two hundred and forty-five 3 月 4 日至
极好的 斋浦尔 Five thousand four hundred Five hundred and forty-six 7 月 2 日至
Mno 无聊死了 Seven thousand eight hundred Four hundred and thirty-two 6 月 7 日至
Jkl 斋浦尔 Five thousand four hundred Seven hundred and sixty-eight 7 月 9 日至
负载匹配网络（Load Matching Network） 德里 Seven thousand eight hundred Nine hundred and eighty-seven 6 月 8 日至
Ijk 斋浦尔 Six thousand seven hundred Six hundred and fifty-four 6 月 5 日至

  1. COUNT() Example : The following SQL statement finds the number of Names in the “GeeksTab” table :

    sql SELECT COUNT(Name) FROM GeeksTab;

    输出–

    sql 7

  2. AVG() Example : The following SQL statement finds the average price of salary in the “GeeksTab” table :

    sql SELECT AVG(Salary) FROM GeeksTab;

    输出–

    sql 6300

  3. SUM() Example : The following SQL statement will find the sum of the Salary in the “GeeksTab” table :

    sql SELECT SUM(Salary) FROM GeeksTab;

    输出–

    sql 44100

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