一个INNER JOIN
就足够了您的需求。MysqL没有PIVOT
功能,您仍然可以使用CASE
和MAX()
功能对其进行仿真。
SELECT a.ID, a.NAME,
MAX(CASE WHEN b.Race_Number = 1 THEN b.Place ELSE NULL END) Race1,
MAX(CASE WHEN b.Race_Number = 2 THEN b.Place ELSE NULL END) Race2,
MAX(CASE WHEN b.Race_Number = 3 THEN b.Place ELSE NULL END) Race3
FROM Table1 a
INNER JOIN Table2 b
ON a.ID = b.ID
GROUP BY a.ID, a.Name
但是,如果您不知道的数量RACE
,则DYNAMIC sql
首选a。
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT('MAX(CASE WHEN b.Race_Number = ', Race_Number,
' THEN b.Place END) AS ', CONCAT('`Race', Race_Number, '`'))
) INTO @sql
FROM Table2;
SET @sql = CONCAT('SELECT s.Student_name, ', @sql, '
FROM Table1 a
LEFT JOIN Table2 b
ON ON a.ID = b.ID
GROUP BY a.ID, a.Name');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;