如何检索mysql的多列数据

Question

表名是Test.Contain三列id，category，units

Inserted values are:(101,a,10),(102,b,30),(101,a,20).

在'a'和id=101单位的类别中countsum 'a'出现了多少次。

预期输出为(resultset):totala=2，counttotal=30 (2,30)。

Answer 1

尝试此查询

SELECT COUNT(*) AS rows, SUM(units) AS counttotal
FROM Test
WHERE id= '101';

Answer 2

试试这个

SELECT COUNT（category）as totala，SUM（units）as counttotal FROM Test WHERE category =＆＃39; a＆＃39; GROUP BY id

Answer 3

试试这个

SELECT id, COUNT(category), SUM(units) FROM Test GROUP BY id

Answer 4

试试这种方式

SELECT COUNT（id）AS totala，SUM（单位）AS counttotal FROM Test WHERE category =＆＃39; a＆＃39; GROUP BY id

Answer 5

SELECT COUNT( category ) , SUM( units ) 
FROM  `test` 
WHERE id =  '101'
GROUP BY category

Answer 6

SELECT
   COUNT(id) AS total_count, SUM(units) AS total_units
FROM
   Test
WHERE
   id= '101' AND units = 'a';