在MariaDB / MySQL中:
SELECt AVG(dd.val) as median_valFROM (SELECt d.val, @rownum:=@rownum+1 as `row_number`, @total_rows:=@rownum FROM data d, (SELECT @rownum:=0) r WHERe d.val is NOT NULL -- put some where clause here ORDER BY d.val) as ddWHERe dd.row_number IN ( FLOOR((@total_rows+1)/2), FLOOR((@total_rows+2)/2) );
史蒂夫·科恩(Steve Cohen)指出,在第一遍之后,@
rownum将包含行的总数。这可用于确定中位数,因此不需要第二遍或连接。
另外
AVG(dd.val),
dd.row_number IN(...)当记录数为偶数时,用于正确产生中位数。推理:
SELECT FLOOR((3+1)/2),FLOOR((3+2)/2); -- when total_rows is 3, avg rows 2 and 2SELECT FLOOR((4+1)/2),FLOOR((4+2)/2); -- when total_rows is 4, avg rows 2 and 3
最后,MariaDB 10.3.3+包含MEDIAN函数



