MySQL查询平均值

Question

早上好。 我有这张桌子：

mysql> select * from Data;
+---------------------------+--------+-------+
| affyId                    | exptId | level |
+---------------------------+--------+-------+
| 31315_at                  | 3      |   250 |
| 31324_at                  | 3      |    91 |
| 31325_at                  | 1      |   191 |
| 31325_at                  | 2      |   101 |
| 31325_at                  | 4      |    51 |
| 31325_at                  | 5      |    71 |
| 31325_at                  | 6      |    31 |
| 31356_at                  | 3      |    91 |
| 31362_at                  | 3      |   260 |
| 31510_s_at                | 3      |   257 |
| 5321_at                   | 4      |    90 |
| 5322_at                   | 4      |    90 |
| 5323_at                   | 4      |    90 |
| 5324_at                   | 3      |    57 |
| 5324_at                   | 4      |    90 |
| 5325_at                   | 4      |    90 |
| AFFX-BioB-3_at            | 3      |    97 |
| AFFX-BioB-5_at            | 3      |    20 |
| AFFX-BioB-M_at            | 3      |    20 |
| AFFX-BioB-M_at            | 5      |   214 |
| AFFX-BioB-M_at            | 7      |    20 |
| AFFX-BioB-M_at            | 8      |    40 |
| AFFX-BioB-M_at            | 9      |    20 |
| AFFX-HSAC07/X00351_M_at   | 3      |    86 |
| AFFX-HUMBAPDH/M33197_3_st | 3      |   277 |
| AFFX-HUMTFFR/M11507_at    | 3      |    90 |
| AFFX-M27830_3_at          | 3      |   271 |
| AFFX-MurIL10_at           | 3      |     8 |
| AFFX-MurIL10_at           | 5      |     8 |
| AFFX-MurIL10_at           | 6      |     4 |
| AFFX-MurIL2_at            | 3      |    20 |
| AFFX-MurIL4_at            | 5      |    78 |
| AFFX-MurIL4_at            | 6      |    20 |
| U95-32123_at              | 1      |   128 |
| U95-32123_at              | 2      |   128 |
| U98-40474_at              | 1      |    57 |
| U98-40474_at              | 2      |    57 |
+---------------------------+--------+-------+
37 rows in set (0.00 sec)

如果我想在所有实验中寻找每个阵列探针（affyId）的平均表达水平（level），请执行SELECT affyId, AVG(level) AS average FROM Data GROUP BY affyId;

但是，我无法弄清楚如何为每个实验寻找每个数组探针（affyId）的平均表达水平……这一定与上一个查询类似，但我没有得到很好的结果……有什么帮助吗？

PD：有人告诉我，如果有人解决了我的问题，我应该给我一定的声誉或单击一些绿色按钮...对吗？ 我该怎么做？ 我在这个网站上很新...

Answer 1

只需将其添加到group by子句中

SELECT affyId, exptId, AVG(level) AS average 
FROM Data
GROUP BY affyId, exptId;

Answer 2

这显示每个affyId的平均值：

SELECT affyId, AVG(level) AS average FROM Data GROUP BY affyId

这是每个exptId的平均值：

SELECT exptId, AVG(level) AS average FROM Data GROUP BY exptId

这是每个affyId中每个exptId的平均值：

SELECT affyId, exptId, AVG(level) AS average FROM Data GROUP BY exptId, affyId