SQL:组合具有相同引用ID的记录
我的表中有以下记录SQL:组合具有相同引用ID的记录,sql,sql-server,tsql,select,Sql,Sql Server,Tsql,Select,我的表中有以下记录 ID StudentID Semester Grade 1 1 First 100 2 1 Second 90 3 2 First 90 4 1 Third 85 我想将学生ID 1的所有记录合并到一个记录中 StudentID First Second Third 1 100
ID StudentID Semester Grade
1 1 First 100
2 1 Second 90
3 2 First 90
4 1 Third 85
我想将学生ID 1的所有记录合并到一个记录中
StudentID First Second Third
1 100 90 85
2 90 null null
有什么想法吗?既然你没有提到你正在使用什么RDBMS,那就试试这个
SELECT StudentID,
MAX(CASE WHEN Semester = 'First' THEN Grade ELSE NULL END) AS First,
MAX(CASE WHEN Semester = 'Second' THEN Grade ELSE NULL END) AS Second,
MAX(CASE WHEN Semester = 'Third' THEN Grade ELSE NULL END) AS Third
FROM tableName
GROUP BY StudentID