DISTINCT
: Returns
a one-column table that contains the distinct values from the specified column. DISTINCT
is an optional keyword that precedes the list of columns specified in the
SELECT clause.
The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement.
Note:
1. When only one expression is provided in the DISTINCT clause, the query will return the unique values for that expression.
2. When more than one expression is provided in the DISTINCT clause, the query will retrieve unique combinations for the expressions listed.
3. In SQL, the DISTINCT clause doesn't ignore NULL values. So when using the DISTINCT clause in your SQL statement, your result set will include NULL as a distinct value.
The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement.
Note:
1. When only one expression is provided in the DISTINCT clause, the query will return the unique values for that expression.
2. When more than one expression is provided in the DISTINCT clause, the query will retrieve unique combinations for the expressions listed.
3. In SQL, the DISTINCT clause doesn't ignore NULL values. So when using the DISTINCT clause in your SQL statement, your result set will include NULL as a distinct value.
Example : SELECT with DISTINCT on two
columns
SELECT DISTINCT
agent_code,ord_amount FROM
orders WHERE agent_code='A002';
Example : SELECT with DISTINCT on three
columns
SELECT DISTINCT
agent_code, ord_amount,cust_code
FROM orders WHERE
agent_code='A002';
Example
: SELECT with DISTINCT on all columns of the first query
SELECT DISTINCT agent_code,ord_amount,cust_code,ord_num FROM orders WHERE
agent_code='A002';
Example
: SELECT with DISTINCT on multiple columns and ORDER BY clause
SELECT DISTINCT
agent_code,ord_amount FROM
orders WHERE agent_code='A002'ORDER BY ord_amount;
Example
: COUNT() function and SELECT with DISTINCT on multiple columns.
You can use count() function in a select
statement with distinct on multiple columns to count the distinct rows. Here is
an example :
SELECT COUNT(*)FROM (SELECT DISTINCT agent_code,
ord_amount,cust_code FROM
orders WHERE agent_code='A002');
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