Home Database Mysql Tutorial MySQL DATE_FORMATE函数内置字符集的坑

MySQL DATE_FORMATE函数内置字符集的坑

Jun 07, 2016 pm 05:34 PM
mysql character set

可以看到,随着通过 SET NAMES 修改 character_set_connection、collation_connection 值,DATE_FORMAT() 函数返回结果的字符集也

帮同事处理一个SQL(简化过后的)执行报错:

mysql> select date_format('2013-11-19','Y-m-d') > timediff('2013-11-19', '2013-11-20'); ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,COERCIBLE) and (latin1_swedish_ci,NUMERIC) for operation '>'

乍一看挺莫名其妙的,查了下手册,,发现有这么一段:

The language used for day and month names and abbreviations is controlled by the value of the lc_time_names system variable (Section 9.7, “MySQL Server Locale Support”). The DATE_FORMAT() returns a string with a character set and collation given by character_set_connection and collation_connection so that it can return month and weekday names containing non-ASCII characters.

也就是说,DATE_FORMATE() 函数返回的结果是带有字符集/校验集属性的,而 TIMEDIFF() 函数则没有字符集/校验集属性,我们来验证一下:

mysql> set names utf8; mysql> select charset(date_format('2013-11-19','Y-m-d')), charset(timediff('2013-11-19', '2013-11-20')); +--------------------------------------------+-----------------------------------------------+ | charset(date_format('2013-11-19','Y-m-d')) | charset(timediff('2013-11-19', '2013-11-20')) | +--------------------------------------------+-----------------------------------------------+ | utf8 | binary | +--------------------------------------------+-----------------------------------------------+ mysql> set names gb2312; mysql> select charset(date_format('2013-11-19','Y-m-d')), charset(timediff('2013-11-19', '2013-11-20')); +--------------------------------------------+-----------------------------------------------+ | charset(date_format('2013-11-19','Y-m-d')) | charset(timediff('2013-11-19', '2013-11-20')) | +--------------------------------------------+-----------------------------------------------+ | gb2312 | binary | +--------------------------------------------+-----------------------------------------------+

可以看到,随着通过 SET NAMES 修改 character_set_connection、collation_connection 值,DATE_FORMAT() 函数返回结果的字符集也跟着不一样。在这种情况下,想要正常工作,就需要将结果进行一次字符集转换,例如:

mysql> select date_format('2013-11-19','Y-m-d') > convert(timediff('2013-11-19', '2013-11-20') using utf8); +----------------------------------------------------------------------------------------------+ | date_format('2013-11-19','Y-m-d') > convert(timediff('2013-11-19', '2013-11-20') using utf8) | +----------------------------------------------------------------------------------------------+ | 1 | +----------------------------------------------------------------------------------------------+

就可以了

P.S,MySQL的版本:5.5.20-55-log Percona Server (GPL), Release rel24.1, Revision 217

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Reduce the use of MySQL memory in Docker Reduce the use of MySQL memory in Docker Mar 04, 2025 pm 03:52 PM

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

How to solve the problem of mysql cannot open shared library How to solve the problem of mysql cannot open shared library Mar 04, 2025 pm 04:01 PM

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

How do you alter a table in MySQL using the ALTER TABLE statement? How do you alter a table in MySQL using the ALTER TABLE statement? Mar 19, 2025 pm 03:51 PM

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

Run MySQl in Linux (with/without podman container with phpmyadmin) Run MySQl in Linux (with/without podman container with phpmyadmin) Mar 04, 2025 pm 03:54 PM

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

What is SQLite? Comprehensive overview What is SQLite? Comprehensive overview Mar 04, 2025 pm 03:55 PM

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

Running multiple MySQL versions on MacOS: A step-by-step guide Running multiple MySQL versions on MacOS: A step-by-step guide Mar 04, 2025 pm 03:49 PM

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

How do I configure SSL/TLS encryption for MySQL connections? How do I configure SSL/TLS encryption for MySQL connections? Mar 18, 2025 pm 12:01 PM

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]

What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)? What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)? Mar 21, 2025 pm 06:28 PM

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

See all articles