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Sql distinct multiple columns

SQL SELECT with DISTINCT on multiple columns

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Description

Multiple fields may also be added with DISTINCT clause. DISTINCT will eliminate those rows where all the selected fields are identical.

Table of contents:

Example : Sample SELECT statement

Here is an simple query on some selected columns in orders table where agent_code='A002'

Sample table : orders

SELECT agent_code, ord_amount, cust_code, ord_num
FROM orders 
WHERE agent_code='A002';

Output

SQL Distinct main

The above picture shows the same agent_code, ord_amount and cust_code appears more than once in the orders table.

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Example : SELECT with DISTINCT on two columns

To get the identical rows (based on two columns agent_code and ord_amount) once from the orders table, the following sql statement can be used :

SELECT  DISTINCT agent_code,ord_amount
FROM orders 
WHERE agent_code='A002';

Output

select disting on two columns.png

Pictorial presentation :

sql distinct on two multiple columns

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Example : SELECT with DISTINCT on three columns

To get the identical rows (based on three columns agent_code, ord_amount and cust_code) once from the orders table , the following sql statement can be used :

SELECT  DISTINCT agent_code, ord_amount,cust_code
FROM orders 
WHERE agent_code='A002';

Output

select disting on three columns

Pictorial presentation :

sql distinct on two multiple columns

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Example : SELECT with DISTINCT on all columns of the first query

To get the identical rows (on four columns agent_code, ord_amount, cust_code and ord_num) once from the orders table , the following sql statement can be used :

SELECT DISTINCT agent_code,ord_amount,cust_code,ord_num  
FROM orders 
WHERE agent_code='A002';

Output

select query with no distinct

In the above output, all rows whose agent_code is 'A002' have returned because there is no identical rows on agent_code, ord_amount, cust_code and ord_num. See the following presentation :

Pictorial presentation :

no distinct query

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SELECT with DISTINCT on multiple columns and ORDER BY clause

You can use an order by clause in select statement with distinct on multiple columns. Here is an example :

SELECT  DISTINCT agent_code,ord_amount
FROM orders 
WHERE agent_code='A002' 
ORDER BY ord_amount;

Output

select distinct multiple columns with order by

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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');

Output

select distinct  with count

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SQL Online Practice Editor :




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