UNION in PostgreSQL - Examples & AI Generator

The UNION operator is essential in PostgreSQL for merging results from multiple SELECT queries into a single result set. While powerful, its syntax can trip up even experienced developers—especially when switching between databases or juggling schema nuances. If you’d rather skip manual UNION coding and ensure accurate PostgreSQL syntax every time, AI2sql turns your natural-language instructions into production-ready UNION queries—no coding required.

UNION Syntax in PostgreSQL

Key Features

• Combines results of two or more SELECT queries

• Removes duplicates (use UNION ALL to retain them)

• Column count and types must match in every SELECT

Syntax Structure

SELECT column1, column2 FROM table1
UNION
SELECT column1, column2 FROM table2;

Note: PostgreSQL requires the SELECT statements to have matching column order, count, and compatible data types.

UNION Examples You Can Generate Instantly

• Combine active customers from two regions:

• Get all product names from two product lines (no duplicates):

• List unique order IDs from physical and digital sales:

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• No more syntax errors: AI2sql understands PostgreSQL UNION requirements automatically.

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FAQ - UNION in PostgreSQL

Does UNION keep duplicates?

No, the UNION operator removes duplicates. Use UNION ALL if you want to retain duplicate rows.

Are column names required to be identical?

Column names don’t have to match, but number, order, and data types must be the same in all SELECT statements.

Can I use ORDER BY with UNION?

Yes, but only a single ORDER BY is allowed for the final combined result set, and it must come after the last SELECT.

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