SQL function SQL函数整理及示例

1. AVG()

eg： select avg(column_name) from table_name ;   # 返回数字列的平均值

        select avg(Price) as Pricenum from Products  ;

2. count()

eg: select count(column_name) from table_name ;   # 返回指定列的记录数

      select count(Price) as Pricenum from Products 

3.  max()

eg: select max(column_name) from table_name ;   # 返回数字列的最大值

      select max(Price) as MAX from Products 

  

4. min()

eg: select min(column_name) from table_name ;   # 返回数字列的最小值

      select min(Price) as MIN from Products 

5. sum()

eg: select sum(column_name) from table_name ;   # 返回数字列的和

      select sum(Price) as SUM from Products 

6. group by()

eg: select colunm_name from table_name  where condition group by column;   # 按照某一列的值分组

      select Price  from Products group by Price;  # 按照价格对该列数据进行分组

7. ucase() / upper()

eg: select ucase(column_name) from table_name ;   # 指定列字符大写

      select upper(ProductName) as UPPER from Products 

8. lcase() /lower()

eg: select lcase(column_name) from table_name ;   # 指定列字符小写

      select lower(ProductName) as LOWER from Products 

注： 示例数据库来自于W3School SQL教程， https://www.quanzhanketang.com/sql/trysql_select_all.html?filename=trysql_select_all