5.27. PostgreSQL DISTINCT keyword

发布时间 ：2025-10-25 12:30:48 UTC      

In PostgreSQL DISTINCT Keywords vs. SELECT Statement to remove duplicate records and get only unique records.

When we are usually manipulating data, there may be a situation in which there are multiple duplicate records in a table, and when extracting such records DISTINCT The keyword is particularly meaningful because it only gets a single record, not a duplicate record.

5.27.1. Grammar

Used to remove duplicate records DISTINCT The basic syntax for keywords is as follows:

SELECT DISTINCT column1, column2,.....columnN
FROM table_name
WHERE [condition]

5.27.2. Example

Create COMPANY 表（ 下载 COMPANY SQL 文件 ), the data are as follows:

runoobdb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | James |  24 | Houston   |  10000
(7 rows)

Let’s insert two pieces of data:

INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (8, 'Paul', 32, 'California', 20000.00 );

INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (9, 'Allen', 25, 'Texas', 15000.00 );

Now the figures are as follows:

 id | name  | age | address    | salary
----+-------+-----+------------+--------
  1 | Paul  |  32 | California |  20000
  2 | Allen |  25 | Texas      |  15000
  3 | Teddy |  23 | Norway     |  20000
  4 | Mark  |  25 | Rich-Mond  |  65000
  5 | David |  27 | Texas      |  85000
  6 | Kim   |  22 | South-Hall |  45000
  7 | James |  24 | Houston    |  10000
  8 | Paul  |  32 | California |  20000
  9 | Allen |  25 | Texas      |  15000
(9 rows)

Next, let’s find all the NAME in the COMPANY table:

runoobdb=# SELECT name FROM COMPANY;

The results are as follows:

 name
-------
 Paul
 Allen
 Teddy
 Mark
 David
 Kim
 James
 Paul
 Allen
(9 rows)

Now we’re here. SELECT Statement using the DISTINCT Clause:

runoobdb=# SELECT DISTINCT name FROM COMPANY;

The results are as follows:

name
-------
 Teddy
 Paul
 Mark
 David
 Allen
 Kim
 James
(7 rows)

As you can see from the results, the duplicate data has been deleted.

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