mysql group by之后count
时间: 2023-11-14 20:10:07 浏览: 41
当使用 GROUP BY 语句时,可以使用 COUNT 函数来计算每个分组中的行数。例如,以下 SQL 语句将按照 "name" 列对 "users" 表进行分组,并计算每个分组中的行数:
```
SELECT name, COUNT(*) FROM users GROUP BY name;
```
这将返回一个结果集,其中包含每个不同的 "name" 值以及该值在表中出现的次数。
相关问题
mysql group by count
To use `GROUP BY` with `COUNT` in MySQL, you can count the number of occurrences of a specific column value in each group. Here's an example:
Suppose you have a table called `orders` with columns `product_id` and `quantity`, and you want to count the number of orders for each product. You can use `GROUP BY` along with the `COUNT` function as follows:
```sql
SELECT product_id, COUNT(*) as order_count
FROM orders
GROUP BY product_id;
```
In this example, the `COUNT(*)` function is used to count the number of rows in each group. The result will be a set of rows where each row represents a unique `product_id`, along with the corresponding count of orders (`order_count`) for that product.
You can also add additional columns in the `SELECT` clause if you want to retrieve more information about each product or perform calculations on other columns.
mysql 根据 groupby count 排序
MySQL可以使用GROUP BY关键字对查询结果进行分组,然后使用COUNT函数对每个分组中的行数进行计数。如果需要按计数结果对分组进行排序,可以使用ORDER BY子句,并且在其后面使用COUNT函数的结果作为排序依据。
例如,假设要统计一个表中每个类型的数量,并将结果按数量从大到小排序,可以使用以下查询语句:
SELECT type, COUNT(*) as count FROM table_name GROUP BY type ORDER BY count DESC;
其中,type是要分组的字段,COUNT(*)用于计算每个分组中的行数,count是COUNT函数的别名,ORDER BY count DESC表示按count列的值从大到小排序。查询结果将返回每种类型的数量以及按数量排序后的结果。