MYSQL DISTINCT
MYSQL
The MySQL DISTINCT keyword is used to get only unique (non-duplicate) rows from a table.
MySQL DISTINCT
➔ DISTINCT eliminates redundant data, ensuring that each returned row is unique.
➔ The DISTINCT keyword is used in the SELECT clause.
➔ The DISTINCT keyword should appear immediately after the SELECT keyword.
➔ When multiple columns are specified, DISTINCT uses the combination of values from all listed columns and finds uniqueness.
Syntax
SELECT DISTINCT column1, column2, ...
FROM table_name
WHERE condition;
Customers table structure:
| Field | Type | Null | Key | Default | Extra |
|---|---|---|---|---|---|
| CustomerID | int(11) | NO | PRI | auto_increment | |
| CustomerName | varchar(255) | YES | |||
| ContactName | varchar(255) | YES | |||
| Address | varchar(255) | YES | |||
| City | varchar(255) | YES | |||
| PostalCode | varchar(255) | YES | |||
| Country | varchar(255) | YES |
Example
SELECT DISTINCT Country FROM Customers;
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With multiple columns
➔ With multiple columns, DISTINCT finds unique combinations across all selected columns.
Example
/* DISTINCT on multiple columns. */
SELECT DISTINCT city, state
FROM customers
WHERE country = 'USA';
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COUNT() Function
➔ DISTINCT can be used with COUNT() to count unique values.
Example
SELECT COUNT(DISTINCT Country) FROM Customers;
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