我有下表,我想做以下事情:
-
统计每个项目在表中出现的次数
-
计算的
DISTINCT
项目数 -
按名称对项目进行分组
+-------+---------+ | id | names | +-------+---------+ | 1 | Apple | | 2 | Orange | | 3 | Grape | | 4 | Apple | | 5 | Apple | | 6 | Orange | | 7 | Apple | | 8 | Grape | +-------+---------+
对于1。和3。要点我有以下查询,它运行得很好:
SELECT * , COUNT(names) as count_name, FROM tbl_products WHERE type = '1' GROUP BY names
所以我得到:
Apple (4) Orange (2) Grape (2)
现在,我还想计算按行分组的数量,并添加一行来计算不同的元素,但存在一些问题,因为MySQL接受查询,但无法输出结果:
SELECT * ,
COUNT(names) as count_name,
COUNT(DISTINCT names) as count_total
FROM tbl_products WHERE type = '1'
GROUP BY names
有人能告诉我可能出了什么问题吗?
编辑:为了获得更多的许可,我想得到一张这样的桌子:
+-------+---------+------------+-------------+
| id | names | count_ctg | count_total |
+-------+---------+------------+-------------+
| 1 | Apple | 4 | 3 |
| 2 | Orange | 2 | 3 |
| 3 | Grape | 2 | 3 |
+-------+---------+------------+-------------+
为什么不直接使用您正在使用的查询:
SELECT * ,
COUNT(names) as count_name,
FROM tbl_products WHERE type = '1'
GROUP BY names
此查询实现了所有三个目标。
1) 您可以获得count_name
中每个名称值的数量计数。
2) 不同的names
值的数量将等于结果集中的行数,因为您是按names
分组的。几乎任何客户端MySQL数据库连接库都可以让您检索这个值。
3) 通过明确使用GROUP BY names
,您满足了按名称分组的第三个标准
当然,结果集中id
的值是没有意义的,您可能只想选择names
和count_names
。
1-。统计每个项目在表中出现的次数:
SELECT names, count(names) FROM tbl_products WHERE type = '1' group by names
2-。表中有多少不同的项目:
SELECT DISTINCT names FROM tbl_products WHERE type = '1'
3-。按名称对项目分组:
SELECT count(DISTINCT names) as Total FROM tbl_products WHERE type = '1'
作为您的最后一期(一体化):
SELECT id, names, count(names), total FROM tbl_products, (select count(distinct names) as total from tbl_products) as total WHERE type = '1' group by names
您可以在子查询中获得不同名称的计数,然后OUTER将其重新连接到您已经解决了1和3:的主查询中
SELECT names ,
COUNT(names) as count_name,
Total
FROM tbl_products
OUTER JOIN (SELECT count(DISTINCT names) as Total FROM tbl_products) t2
WHERE type = '1'
GROUP BY names
您可以使用SQL Windowing OVER()
此查询返回row_number()函数作为结果中的id列,row_number的over(…)需要order by子句。你可以随心所欲地点,但大多数都是由某种东西点的。
;WITH vwGroups (name, Quantity) AS
(
SELECT name
, COUNT(*)
FROM tbl_products
GROUP BY name
)
SELECT ROW_NUMBER() OVER(ORDER BY Quantity DESC, name) AS id
, name
, Quantity AS count_name
, COUNT(*) OVER () AS count_total
FROM vwGroups