How Can I Efficiently Check for NULL or Empty Strings in PostgreSQL?

PostgreSQL: Streamlining NULL and Empty String Checks in SQL

Efficiently handling NULL or empty strings within PostgreSQL SQL queries is crucial for performance and code clarity. This guide outlines optimized methods, addressing common pitfalls.

Improving Upon Traditional Methods

The often-used approach:

coalesce( trim(stringexpression),'')=''

while functional, is verbose and inefficient. The trim() function adds unnecessary overhead, particularly for char(n) columns.

Concise and Efficient Solutions

A significantly improved method leverages the following:

(stringexpression = '') IS NOT FALSE

This elegantly checks for both NULL and empty strings without extra function calls. It evaluates to TRUE if the condition holds and NULL if stringexpression is NULL.

Checking for Non-NULL, Non-Empty Strings

For scenarios requiring confirmation of a non-NULL and non-empty string, use:

stringexpression <> ''

This directly checks for inequality with an empty string, returning TRUE if not empty and NULL if NULL.

Handling char(n) Data Type

Remember that char(n) stores empty strings as spaces. However, the methods above correctly handle this peculiarity, working seamlessly across all character data types.

Summary

The suggested expressions offer efficient and readable solutions for NULL and empty string checks in PostgreSQL. Avoiding unnecessary functions enhances query speed and code maintainability.

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