java - mysql query, how to query this

Question

I saw an interview question posted by someone else in the group, =. =, how to query?

Answer 1

The title picture is Chinase, click here.
Course determined case:
CASE implementation:

SELECT
    `Name`,
    MAX(
        CASE
        WHEN Course = 'Chinase' THEN
            Score
        END
    ) AS Chinase,
    MAX(
        CASE
        WHEN Course = 'Math' THEN
            Score
        END
    ) AS Math,
    MAX(
        CASE
        WHEN Course = 'English' THEN
            Score
        END
    ) AS English
FROM
    table1
GROUP BY
    `Name`

IF implementation:

SELECT
    `Name`,

SUM(IF (Course = 'Chinase', Score, 0)) AS Chinase,

SUM(IF (Course = 'Math', Score, 0)) AS Math,

SUM(IF (Course = 'English', Score, 0)) AS English

FROM
    table1
GROUP BY `Name`

Course is not sure, use dynamics:

SET @CC='';
SELECT @CC:=CONCAT(@CC,'SUM(IF(Course=\'',Course,'\'',',Score,0)) AS ',Course,',') FROM (SELECT DISTINCT Course FROM table1) A;
SET @HH=CONCAT('SELECT Name,',LEFT(@CC,LENGTH(@CC)-1),' FROM table1 GROUP BY Name');
PREPARE stmt FROM @HH;
EXECUTE stmt;

Answer 2

select name, sum(case when Course='Chinese' then Score end) as Chinese,
sum(case when type='Math' then Score end) as Math,
sum(case when type='English' then Score end) as English
from table1
group by name

Answer 3

You should learn the principle
Baidu "mysql row column conversion"
It is useless to only learn this sql

Answer 4

This kind of god-like sql is used when doing data statistics. It is not used in normal PHP work.