How Can I Retrieve Only Unique Records from a SQL Database Table?

SQL Techniques for Retrieving Unique Data

Working with large datasets often requires isolating unique records to eliminate redundancy. This guide demonstrates how to efficiently retrieve only unique entries from your SQL database tables.

Leveraging the DISTINCT Keyword

The DISTINCT keyword is the cornerstone of selecting unique records. Simply place it before the column name(s) you wish to filter for uniqueness. For instance, to obtain unique values from the column2 field in your table, use this SQL query:

<code class="language-sql">SELECT DISTINCT column2 FROM table_name;</code>

This will produce a result set like this:

column2

item1

item2

item3

Note that duplicate item1 entries are removed.

Extending DISTINCT to Multiple Columns

The power of DISTINCT extends to multiple columns, enabling you to identify uniqueness based on combinations of field values. To retrieve unique rows based on both column2 and column3, the query would be:

<code class="language-sql">SELECT DISTINCT column2, column3 FROM table_name;</code>

This ensures that only rows with unique pairings of column2 and column3 values are returned.

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