SQL | Distinct Clause
The distinct keyword is used in conjunction with select keyword. It is helpful when there is a need of avoiding duplicate values present in any specific columns/table. When we use distinct keyword only the unique values are fetched.
SELECT DISTINCT column1, column2 FROM table_name
column1, column2 : Names of the fields of the table.
table_name : Table from where we want to fetch the records.
This query will return all the unique combinations of rows in the table with fields column1, column2.
NOTE: If distinct keyword is used with multiple columns, the distinct combination is displayed in the result set.
Table – Student
ROLL_NO NAME ADDRESS PHONE AGE 1 RAM DELHI XXXXXXXXXX 18 2 RAMESH GURGAON XXXXXXXXXX 18 3 SUJIT ROHTAK XXXXXXXXXX 20 4 SURESH DELHI XXXXXXXXXX 18 3 SUJIT ROHTAK XXXXXXXXXX 20 2 RAMESH GURGAON XXXXXXXXXX 18
- To fetch unique names from the NAME field –
SELECT DISTINCT NAME FROM Student;
NAME Ram RAMESH SUJIT SURESH
- To fetch a unique combination of rows from the whole table –
SELECT DISTINCT * FROM Student;
ROLL_NO NAME ADDRESS PHONE Age 1 Ram Delhi XXXXXXXXXX 18 2 RAMESH GURGAON XXXXXXXXXX 18 3 SUJIT ROHTAK XXXXXXXXXX 20 4 SURESH Delhi XXXXXXXXXX 18
Note : Without the keyword distinct in both the above examples 6 records would have been fetched instead of 4, since in the original table there are 6 records with the duplicate values.
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