July 17th, 2013 
Jijo K Jose My database contents
| ID | CLASS_CODE | ROLL_NO | NAME |
|---|---|---|---|
| 1 | IX | 1 | Jijo K Jose |
| 2 | IX | 3 | James Jacob |
| 3 | X | 1 | Joy Mathew |
| 4 | X | 2 | Sam George |
| 5 | IX | 2 | Miller John |
| 6 | X | 3 | Thomas John |
Display values of distinct rows over one column
select distinct(ROLL_NO) from STUDENT;
| ROLL_NO | |
|---|---|
| 1 | |
| 3 | |
| 2 |
Count number of distinct rows over one column
select count(distinct(ROLL_NO)) from STUDENT;
| count(distinct(ROLL_NO)) | |
|---|---|
| 3 |
Display values of distinct rows over multiple column
select distinct CLASS_CODE, ROLL_NO from STUDENT;
| CLASS_CODE | ROLL_NO | |
|---|---|---|
| IX | 1 | |
| IX | 3 | |
| X | 1 | |
| X | 2 | |
| IX | 2 | |
| X | 3 |
Count number of distinct rows over multiple column
select count(*) from (select distinct CLASS_CODE, ROLL_NO from STUDENT) TEMP;
| count(*) | |
|---|---|
| 6 |
