Seems like there are so many places where these things are set: database connection/server, wp-config.php, the database, each table, and each column. Well I certainly don’t really know what I’m doing. Do I have a problem? I’ve seen a lot of different ideas about how to fix this if necessary, and would appreciate some authoritative pointers. Utf8_general_ci (all WP core and Wordfence tables) Utf8mb4_unicode_520_ci (only one plugin table has this) But the tables have a variety of collations: utf8mb4_unicode_ci (tables of 2 plugins) In phpMyAdmin, it shows Server connection collation is “utf8mb4_unicode_ci”, and Server charset is “UTF8 Unicode (utf8mb4)”. wp-config.php has: define('DB_CHARSET', 'utf8') Someone told me this indicates a problem in my database, that I have the wrong character set and/or collation. WordPress database error Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8mb4_unicode_ci,COERCIBLE) for operation 'like' for query SELECT SQL_CALC_FOUND_ROWS wp75_posts.ID FROM wp75_posts WHERE 1=1 AND wp75_posts.ID NOT IN (5729,5709,4178,2170,2433,1966,1908,1800,650,76) AND (((wp75_posts.post_title LIKE. It began like this, followed by a bunch of spam content: Recently an error showed up in debug log when someone tried to spam my site. About 6 months ago I migrated to a different host. WHERE llation_name = T.My site has been on WordPress just over 3 years I think. Information_schema.`COLLATION_CHARACTER_SET_APPLICABILITY` CCSA Here’s how to check the database settings: SELECT SCHEMA_NAME 'database',Īnd to modify it: ALTER DATABASE neocamino CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci Ĭheck the settings: SELECT table_name, CCSA.character_set_name, llation_name For Rails developper, you can set it in your config/database.yml file: # config/database.yml For latin1: latin1_swedish_ci (case-insensitive) or latin1_binįor the examples below I’ll use a database called “neocamino”.For utf8: utf8_general_ci (case-insensitive) or utf8_bin.For utf8mb4: utf8mb4_unicode_ci (case-insensitive) or utf8mb4_bin.Your text content won’t have such special characters: latin1.You care about accents but not smileys: utf8.You care about accents and smileys: utf8mb4.For a case-sensitive collation, go for latin1_general_cs or latin1_bin. The default collation for latin1 encoding is latin1_swedish_ci (notice the “_ci” at the end). You’ll have to work around that in your queries. There doesn’t seem to be a collation that ignores case but not accents ( utf8_general_cs, for “case-sensitive”, is experimental and might not work for you). If you care about accents, go for utf8_bin (or utf8mb4_bin). With such a collation, lower/upper case and accents will be ignored in your searches and constraints on text columns. Notice the “_ci” part at the end? It means “case insensitive” and implicitly also “accents insensitive”. With utf8 you usually go with utf8_general_ci (or utf8mb4_unicode_ci with utf8mb4). If a query for “deja vu” should match records like “déjà vu”, you’ll want an accent-insensitive collation. If a query for “hello” should match records like “HeLLo”, you’ll want a case-insensitive collation. How about the collation?Īgain, the collation is used when comparing data, for example in a WHERE clause (equal or LIKE), or with unicity constraints on text columns. More info in this excellent article on the matter. So if a column was a varchar(256) in utf8, it should now be a varchar(191) in utf8mb4. That changes the maximum length a column or index can hold. In utf8mb4, we add an extra byte to store special characters like smileys. In utf8, a character can be encoded in a maximum of 3 bytes. NB: a note of warning when migrating from utf8 to utf8mb4. If you don’t care about any of that, simply go with the default, latin1. For that you’ll need utf8mb4, available since MySQL 5.5.3. Be careful, this encoding won’t handle smileys. If you need to handle special characters, like letters with accents, people will usually tell you to go for a utf8 encoding. You’ll find SQL commands at the end of this article to check and modify that. Note that you can set both encoding and collation at the server level, at the database level, at the table level or even for particular columns only. The collation is used when comparing data, for example in a WHERE clause (equal or LIKE), or with unicity constraints on text columns. Here’s a quick guide on how to choose your encoding and the collation right from the start, and avoid the pain of debugging your encoding issues. You generally start with the defaults and fix issues along the way.
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