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https://dev.mysql.com/doc/refman/5.7/en/exists-and-not-exists-subqueries.html
If a subquery returns any rows at all, EXISTS subquery is TRUE, and NOT EXISTS subquery is FALSE. For example: SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2); Traditionally, an EXISTS subquery starts with SELECT *, but it could begin with ...MySQL ignores the SELECT list in such a subquery, so it makes no ...
https://dev.mysql.com/doc/refman/5.7/en/sys-table-exists.html
Tests whether a given table exists as a regular table, a TEMPORARY table, or a view. If both a temporary and a permanent table exist with the given name, TEMPORARY is returned. Parameters in_db VARCHAR(64): The name of the database in which to ...
https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html
It controls whether the server autogenerates SSL key and certificate files in the data directory, if they do not already exist. For example, if you bind the server to *, you can connect to it using all existing accounts. ENGINE to change the storage ... The MySQL server maintains many system variables that affect its ...
https://dev.mysql.com/doc/refman/5.7/en/subquery-optimization-with-exists.html
The converted comparison looks like this: EXISTS (SELECT 1 FROM ... Roughly speaking, the subquery can be converted to something like this: EXISTS (SELECT 1 FROM ... WHERE subquery_where) Be converted to this expression that uses a pushed-down ...
https://dev.mysql.com/doc/refman/5.7/en/replication-features-create-if-not-exists.html
IF NOT EXISTS statements are replicated: Every CREATE DATABASE IF NOT EXISTS statement is replicated, whether or not the database already exists on the source. Similarly, every CREATE TABLE IF NOT EXISTS statement without a SELECT is replicated, ...
https://dev.mysql.com/doc/refman/5.7/en/replication-features-drop-if-exists.html
The DROP DATABASE IF EXISTS, DROP TABLE IF EXISTS, and DROP VIEW IF EXISTS statements are always replicated, even if the database, table, or view to be dropped does not exist on the source. This is to ensure that the object to be dropped no longer ...
https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html
A path-value pair for an existing path in the document is ignored and does not overwrite the existing document value. A path-value pair for a nonexisting path in the document adds the value to the document if the path identifies one of these types ... The functions in this section modify JSON values and return the ...
https://dev.mysql.com/doc/refman/5.7/en/replication-howto-additionalslaves.html
You can add another replica to an existing replication configuration without stopping the source server. To do this, you can set up the new replica by copying the data directory of an existing replica, and giving the new replica a different server ...You can do this by creating an archive using tar or WinZip, or by performing a direct copy using a tool such as cp or ...
https://dev.mysql.com/doc/refman/5.7/en/create-table.html
An error occurs if the table exists, if there is no default database, or if the database does not exist. This works regardless of whether there is a default database, assuming that the database exists. IF NOT EXISTS Prevents an error from occurring ...| {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...) [index_option] ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-index-stat.html
To force them to be created (or updated if they already exist), invoke ndb_index_stat with the --update option, or execute ANALYZE TABLE on the table in the mysql client. --sys-create-if-not-exist Command-Line Format --sys-create-if-not-exist Create ... ndb_index_stat provides per-fragment statistical information about indexes on NDB ...