MySQL常用聚合函数

官方文档：Aggregate (GROUP BY) Functions 

Name	Description
AVG()	Return the average value of the argument
BIT_AND()	Return bitwise AND
BIT_OR()	Return bitwise OR
BIT_XOR()	Return bitwise XOR
COUNT()	Return a count of the number of rows returned
COUNT(DISTINCT)	Return the count of a number of different values
GROUP_CONCAT()	Return a concatenated string
MAX()	Return the maximum value
MIN()	Return the minimum value
STD()	Return the population standard deviation
STDDEV()	Return the population standard deviation
STDDEV_POP()	Return the population standard deviation
STDDEV_SAMP()	Return the sample standard deviation
SUM()	Return the sum
VAR_POP()	Return the population standard variance
VAR_SAMP()	Return the sample variance
VARIANCE()	Return the population standard variance

1.AVG

AVG(col)

返回指定列的平均值

2.COUNT

COUNT(col)

返回指定列中非NULL值的个数

 

3.MIN/MAX

MIN(col)：返回指定列的最小值

MAX(col)：返回指定列的最大值

4.SUM

SUM(col)

返回指定列的所有值之和

5.GROUP_CONCAT

GROUP_CONCAT([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [SEPARATOR str_val])

返回由属于一组的列值连接组合而成的结果

SELECT id,GROUP_CONCAT(name) FROM my_table GROUP BY id;
SELECT id,GROUP_CONCAT(name SEPARATOR ';') FROM my_table GROUP BY id;
SELECT id,GROUP_CONCAT(DISTINCT name SEPARATOR ';') FROM my_table GROUP BY id;
SELECT id,GROUP_CONCAT(name order by id) FROM my_table GROUP BY id;
SELECT id,GROUP_CONCAT(name order by id SEPARATOR ';') FROM my_table GROUP BY id;

　　

注：MySQL默认对结果限制在1024，会自动截断，可以通过变量group_concat_max_len设置，坑！！