===01【###group by 多个字段,字段顺序对查询结果数据没有影响,只是record顺序不同而已】 group by 后面的字段顺序 只是影响了结果的顺序 不会影响结果的值。 如果是 group by a,b 那么就是按照 order by a,b 的顺序分组,因为分组是需要先排序的 反之group by b,a 就是按照b,a的顺序分组 案例: --> ...
可以使用 MySQL 的 GROUP BY 和 SUM 函数来快速求出每一列的总和。下面是一个示例语句: SELECT SUM(column_1), SUM(column_2), SUM(column_3), ... FROM table_name GROUP BY column_name; 1. 其中,table_name 是表名,column_1, column_2, column_3, ... 是要求和的列名,column_name 是分组依...
selectcount(colName)from table_name;# 指定列 2.SUM指令: 针对数字类型进行求和的算数运算 代码语言:javascript 复制 selectsum(colName'数字类型的字段')from table_name; 3.AVG 指令: 支持数字类型进行平均值的算数运算 代码语言:javascript 复制 selectsum(colName'数字类型的字段')from table_name; 4.MAX和...
TABLE_NAME, TABLE_COMMENT FROM information_schema.TABLES WHERE 1=1 # AND TABLE_SCHEMA = '数据库...
mysql 亿级数据量 ( sum ,group by )的优化 今天开发提出需求,让统计数据,一询问才得知表中的数据量已达亿级以上。具体的sql如下: SELECTid_province_code,gender,age,COUNT(1),SUM(zy_days),SUM(zf),SUM(ybnje)FROMmedicare2017WHEREzy_enter_dateBETWEEN'2017-01-01 00:00:00'AND'2017-12-31 12:59...
biiv.VendorID = '1' GROUP BY biiv.ItemVendorID order by yearmonth, shortname asc Subject Written By Posted SUM DISTINCT multiple columns Joel Pearson June 27, 2007 03:09AM Sorry, you can't reply to this topic. It has been closed....
2:sum ①select sum(chinese) from exam_result; chinese那一列全部相加,sum()函数中null会忽略掉,但在SQL中null与其他数字进行运算时,结果一般都是null。 编辑 编辑 ②select sum(name) from exam_result; sql把字符串当做数字进行算术运算,都会尝试把字符串转化为数字,但是汉字不行 ...
比如我们的数据库信息如下(sex中1表示男生,0表示女生): msg_info 表格 name age sex Los 20 1 San 25 0 Lan 30 0 Bos 23 1 mini 28 1 于是我们我们的sql语句就形成了: SELECT sex,sum(age) FROM `msg_info` group by sex 结果: sex sum(age) 0 55 1 71...
SELECT table_schema AS '数据库', sum( table_rows ) AS '记录数', sum( TRUNCATE ( data_length / 1024 / 1024, 2 )) AS '数据容量(MB)', sum( TRUNCATE ( index_length / 1024 / 1024, 2 )) AS '索引容量(MB)' FROM information_schema.TABLES GROUP BY table_schema ORDER BY sum( data...
Sum Count Max Min Group_concat First Last 37. What does a group_concat() do? The Group_concat function virtually groups and combines multiple rows into a single row. For example, the below Query to get all the actors for documentary movies. SELECT F.TITLE,F.DESCRIPTION,F.LENGTH,F.RATING...