NULL value first ascending sort in PostgreSQL
When sorting in ascending order in a PostgreSQL table, you usually want to prioritize records containing NULL values over records with non-NULL values. This is particularly important when dealing with date/time fields that allow empty or NULL input.
PostgreSQL provides the convenient ORDER BY
modifier in the NULLS FIRST
statement to solve this problem. Using this modifier ensures that records with NULL values appear before records with non-NULL values in an ascending sort operation.
Here is a sample query:
ORDER BY last_updated ASC -- NULL 值的 last_updated 记录排在最后?
You can add the NULLS FIRST
modifier to this query to get the desired results:
ORDER BY last_updated ASC NULLS FIRST
It should be noted that PostgreSQL also provides the NULLS LAST
modifier. This modifier does the opposite; it ensures that NULL-valued records appear after non-NULL-valued records in an ascending sort.
NULLS FIRST
and NULLS LAST
modifiers can significantly increase the flexibility and control of PostgreSQL sort operations. They enable users to handle NULL values in a way that suits their specific requirements, ensuring that non-NULL values appear after or before NULL values in an ascending sort, as appropriate.
The above is the detailed content of How to Sort Data in PostgreSQL with NULLs First in Ascending Order?. For more information, please follow other related articles on the PHP Chinese website!

This article explores optimizing MySQL memory usage in Docker. It discusses monitoring techniques (Docker stats, Performance Schema, external tools) and configuration strategies. These include Docker memory limits, swapping, and cgroups, alongside

This article addresses MySQL's "unable to open shared library" error. The issue stems from MySQL's inability to locate necessary shared libraries (.so/.dll files). Solutions involve verifying library installation via the system's package m

The article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.

This article compares installing MySQL on Linux directly versus using Podman containers, with/without phpMyAdmin. It details installation steps for each method, emphasizing Podman's advantages in isolation, portability, and reproducibility, but also

This article provides a comprehensive overview of SQLite, a self-contained, serverless relational database. It details SQLite's advantages (simplicity, portability, ease of use) and disadvantages (concurrency limitations, scalability challenges). C

Article discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]

This guide demonstrates installing and managing multiple MySQL versions on macOS using Homebrew. It emphasizes using Homebrew to isolate installations, preventing conflicts. The article details installation, starting/stopping services, and best pra

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Linux new version
SublimeText3 Linux latest version

Notepad++7.3.1
Easy-to-use and free code editor

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Dreamweaver CS6
Visual web development tools
