SELECT column FROM table
ORDER BY RAND()
LIMIT 10
Code language: SQL (Structured Query Language) (sql)SELECT column FROM
( SELECT column FROM table
ORDER BY dbms_random.value )
WHERE rownum <= 10
[/code]
<h2>Select random rows in PostgreSQL</h2>
<!-- wp:code {"language": "sql"} --><pre class="wp-block-code"><code></code></pre><!-- /wp:code -->
SELECT column FROM table
ORDER BY RANDOM()
LIMIT 10
Code language: SQL (Structured Query Language) (sql)SELECT TOP 10 column FROM table
ORDER BY NEWID()
Code language: SQL (Structured Query Language) (sql)Java URL Encoder/Decoder Example - In this tutorial we will see how to URL encode/decode…
Show Multiple Examples in OpenAPI - OpenAPI (aka Swagger) Specifications has become a defecto standard…
Local WordPress using Docker - Running a local WordPress development environment is crucial for testing…
1. JWT Token Overview JSON Web Token (JWT) is an open standard defines a compact…
GraphQL Subscription provides a great way of building real-time API. In this tutorial we will…
1. Overview Spring Boot Webflux DynamoDB Integration tests - In this tutorial we will see…
View Comments
Oracle solution should be WHERE rownum <= 10
Good Catch Rich..
Thanks for pointing out the typo.. I updated the query.
That is a really bad way to get random rows from a table. It always requires a full table scan.
This guy's blog has some alternate ideas for MySQL:
http://www.titov.net/2005/09/21/do-not-use-order-by-rand-or-how-to-get-random-rows-from-table/
and here:
http://www.mysqlperformanceblog.com/2006/09/01/order-by-limit-performance-optimization/#comment-2838
Order by rand has bad performance with big tables.
There is another way to produce random rows using only a query and without order by rand().
It involves User Defined Variables.
See http://www.mysqldiary.com/how-to-produce-random-rows-from-a-table/
Thanks a lot. Your solution works as required.
THANKS Rich for updating about the Oracle .........
In order to find random rows from a table, don’t use ORDER BY RAND() because it forces MySQL to do a full file sort and only then to retrieve the limit rows number required. In order to avoid this full file sort, use the RAND() function only at the where clause. It will stop as soon as it reaches to the required number of rows.
See
http://www.rndblog.com/how-to-select-random-rows-in-mysql/
thank you very much!
below query selects only two records from the list of agents..i.e 2 random records for each agent over the span of a week etc.... it works !!
with summary as ( Select Dbms_Random.Random As Ran_Number, colmn1, colm2, colm3 Row_Number() Over(Partition By col2 Order By Dbms_Random.Random) As Rank From table1, table2 Where Table1.Id = Table2.Id Order By Dbms_Random.Random Asc) Select tab1.col2, tab1.col4, tab1.col5, From Summary s Where s.Rank <= 2;
Can any one tell me the SQL Server Query to retrieve random records from more than one table(2 or more).