The SQL
DISTINCT keyword is used in conjunction with SELECT statement to eliminate all the duplicate records and fetching only unique records.
There may be a situation when you have multiple duplicate records in a
table. While fetching such records, it makes more sense to fetch only
unique records instead of fetching duplicate records.
Syntax:
SELECT DISTINCT column1, column2,.....columnN
FROM table_name
WHERE [condition]
|
Example:
Consider CUSTOMERS table is having following records:
+----+----------+-----+-----------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+-----------+----------+
| 1 | Ramesh | 32 | Ahmedabad | 2000.00 |
| 2 | Khilan | 25 | Delhi | 1500.00 |
| 3 | kaushik | 23 | Kota | 2000.00 |
| 4 | Chaitali | 25 | Mumbai | 6500.00 |
| 5 | Hardik | 27 | Bhopal | 8500.00 |
| 6 | Komal | 22 | MP | 4500.00 |
| 7 | Muffy | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
|
First let us see how the following SELECT query returns duplicate salary records:
SQL> SELECT SALARY FROM CUSTOMERS
ORDER BY SALARY;
|
This would produce following result where salary 2000 is coming twice which is a duplicate record from the original table.
+----------+
| SALARY |
+----------+
| 1500.00 |
| 2000.00 |
| 2000.00 |
| 4500.00 |
| 6500.00 |
| 8500.00 |
| 10000.00 |
+----------+
|
Now let us use DISTINCT keyword with the above SELECT query and see the result:
SELECT DISTINCT SALARY FROM CUSTOMERS
ORDER BY SALARY;
|
This would produce following result where we do not have any duplicate entry:
+----------+
| SALARY |
+----------+
| 1500.00 |
| 2000.00 |
| 4500.00 |
| 6500.00 |
| 8500.00 |
| 10000.00 |
+----------+
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