How Can I Randomly Select Rows in SQL?

SQL random row selection

When processing large data sets, it may be necessary to randomly select a subset of rows for processing or analysis. SQL provides several ways to accomplish this task.

Microsoft SQL Server

A common way to randomly select rows in Microsoft SQL Server is to use the NEWID() function. The following query retrieves 5 random rows of data from the customerNames table:

<code class="language-sql">SELECT TOP 5 Id, Name
FROM customerNames
ORDER BY NEWID()</code>

The NEWID() function generates a globally unique identifier (GUID) that changes each time the query is executed, ensuring a different set of rows is returned each time.

Other SQL implementations

Other SQL implementations use different syntax to randomly select rows. The following table provides examples of commonly used databases:

数据库	语法
MySQL	ORDER BY RAND()
PostgreSQL	ORDER BY RANDOM()
Oracle	ORDER BY dbms_random.value
SQLite	ORDER BY RANDOM()
IBM DB2	ORDER BY RAND()

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