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* Additional .gitignore entries * Merge a bunch of small articles about system tables into single one * Merge a bunch of small articles about formats into single one * Adapt table with formats to English docs too * Add SPb meetup link to main page * Move Utilities out of top level of docs (the location is probably not yet final) + translate couple articles * Merge MacOS.md into build_osx.md * Move Data types higher in ToC * Publish changelog on website alongside documentation * Few fixes for en/table_engines/file.md * Use smaller header sizes in changelogs * Group up table engines inside ToC * Move table engines out of top level too * Specificy in ToC that query language is SQL based. Thats a bit excessive, but catches eye. * Move stuff that is part of query language into respective folder * Move table functions lower in ToC * Lost redirects.txt update * Do not rely on comments in yaml + fix few ru titles * Extract major parts of queries.md into separate articles * queries.md has been supposed to be removed * Fix weird translation * Fix a bunch of links * There is only table of contents left * "Query language" is actually part of SQL abbreviation * Change filename in README.md too * fix mistype
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MySQL
The MySQL engine allows you to perform SELECT queries on data that is stored on a remote MySQL server.
The engine takes 5-7 parameters: the server address (host and port); the name of the database; the name of the table; the user's name; the user's password; whether to use replace query; the on duplcate clause. Example:
MySQL('host:port', 'database', 'table', 'user', 'password'[, replace_query, 'on_duplicate_clause']);
At this time, simple WHERE clauses such as =, !=, >, >=, <, <= are executed on the MySQL server.
The rest of the conditions and the LIMIT sampling constraint are executed in ClickHouse only after the query to MySQL finishes.
If replace_query is specified to 1, then INSERT INTO query to this table would be transformed to REPLACE INTO.
If on_duplicate_clause is specified, eg update impression = values(impression) + impression, it would add on_duplicate_clause to the end of the MySQL insert sql.
Notice that only one of 'replace_query' and 'on_duplicate_clause' can be specified, or none of them.