Question

how to get count based on enum status using self join

I have a table called “student” in which I have used enum for status 0,1,2 where 0 for inactive, 1 for active and 2 for deleted.

that is

studentid studentenrollid studentname studentstatus

1          3                 xyz          1

2          3                 xyz          2

3          8                 asda         1

4          7                 sdd          1

5          9                 asds         0

6          3                 xyz          1

I need get the count based on status where studentrollid is unique.

studentrollid | inactive | active | deleted

    3            0           2        1

    8            0           1        0

    7            0           1        0

    9            1           0        0

Answer 1

Try this please:

SQLFIDDLE DEMO

select studentenrollid,
sum(case when studentstatus = 1 then 1
    else 0 end) as Active, 
sum(case when studentstatus = 0 then 1
    else 0 end) as Inactive, 
sum(case when studentstatus = 2 then 1
    else 0 end) as Deleted
from demo
group by studentenrollid
;

| STUDENTENROLLID | ACTIVE | INACTIVE | DELETED |
-------------------------------------------------
|               3 |      2 |        0 |       1 |
|               7 |      1 |        0 |       0 |
|               8 |      1 |        0 |       0 |
|               9 |      0 |        1 |       0 |

Another shorter query:

select a.studentenrollid,
sum(a.studentstatus = 1) as Active, 
sum(a.studentstatus = 0) as Inactive,
sum(a.studentstatus = 2) as Deleted 
from demo a
group by a.studentenrollid
;

| STUDENTENROLLID | ACTIVE | INACTIVE | DELETED |
-------------------------------------------------
|               3 |      2 |        0 |       1 |
|               7 |      1 |        0 |       0 |
|               8 |      1 |        0 |       0 |
|               9 |      0 |        1 |       0 |

MYSQL 5.1.61 version query

---

Based on OP’s create statment/insert statements given in the comments:

SQLFIDDEL DEMO 2

| STUDENTENROLLID | ACTIVE | INACTIVE | DELETED |
-------------------------------------------------
|               1 |      1 |        0 |       0 |
|               2 |      1 |        0 |       0 |
|               3 |      1 |        0 |       0 |
|              41 |      9 |        1 |       1 |