【MYSQL】select from group by

mysql> select * from t_user group by lvl;
+-----+-------+----------+------+--------+
| uid | uname | tel      | lvl  | salart |
+-----+-------+----------+------+--------+
|   1 | alex  | 23131231 | A    |   1100 |
|   3 | kit   | 87416574 | B    |   1200 |
|   4 | poker | 41874521 | C    |   1560 |
+-----+-------+----------+------+--------+
mysql> select lvl from t_user group by lvl;
+------+
| lvl  |
+------+
| A    |
| B    |
| C    |
+------+

mysql> select lvl,group_concat(salart) from t_user group by lvl;
+------+----------------------+
| lvl  | group_concat(salart) |
+------+----------------------+
| A    | 1100,4300            |
| B    | 1200                 |
| C    | 1560                 |
+------+----------------------+
3 rows in set (0.00 sec)

mysql> select lvl,group_concat(uid) as salary from t_user group by lvl;
+------+--------+
| lvl  | salary |
+------+--------+
| A    | 1,2    |
| B    | 3      |
| C    | 4      |
+------+--------+
3 rows in set (0.00 sec)

mysql> select lvl,group_concat(salart) from t_user group by lvl;
+------+----------------------+
| lvl  | group_concat(salart) |
+------+----------------------+
| A    | 1100,4300            |
| B    | 1200                 |
| C    | 1560                 |
+------+----------------------+
3 rows in set (0.00 sec)

mysql> select lvl,group_concat(salart) as salary from t_user group by lvl;
+------+-----------+
| lvl  | salary    |
+------+-----------+
| A    | 1100,4300 |
| B    | 1200      |
| C    | 1560      |
+------+-----------+
3 rows in set (0.00 sec)

mysql> select lvl,group_concat(uid) as salary from t_user group by lvl;
+------+--------+
| lvl  | salary |
+------+--------+
| A    | 1,2    |
| B    | 3      |
| C    | 4      |
+------+--------+
3 rows in set (0.00 sec)

mysql> select lvl,count(uid) as salary from t_user group by lvl;
+------+--------+
| lvl  | salary |
+------+--------+
| A    |      2 |
| B    |      1 |
| C    |      1 |
+------+--------+
3 rows in set (0.00 sec)

mysql> select lvl,group_concat(salart) from t_user group by lvl having group_concat(salart)=1200;
+------+----------------------+
| lvl  | group_concat(salart) |
+------+----------------------+
| B    | 1200                 |
+------+----------------------+
1 row in set (0.00 sec)

mysql> select lvl,group_concat(salart) from t_user group by lvl having group_concat(salart)=1100;
+------+----------------------+
| lvl  | group_concat(salart) |
+------+----------------------+
| A    | 1100,4300            |
+------+----------------------+
1 row in set (0.00 sec)

mysql> 
mysql> select lvl,count(uid) as salary from t_user group by lvl;
+------+--------+
| lvl  | salary |
+------+--------+
| A    |      2 |
| B    |      1 |
| C    |      1 |
+------+--------+
3 rows in set (0.00 sec)

mysql> select lvl,count(uid) as salary from t_user group by lvl having count(uid)>1;
+------+--------+
| lvl  | salary |
+------+--------+
| A    |      2 |
+------+--------+
1 row in set (0.00 sec)