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Search Results
https://dev.mysql.com/doc/refman/8.0/en/no-matching-rows.html
If you have a complicated query that uses many tables but that returns no rows, you should use the following procedure to find out what is wrong: Test the query with EXPLAIN to check whether you can find something that is obviously wrong. Select ...
https://dev.mysql.com/doc/refman/8.0/en/partitioning-limitations-partitioning-keys-unique-keys.html
This section discusses the relationship of partitioning keys with primary keys and unique keys. The rule governing this relationship can be expressed as follows: All columns used in the partitioning expression for a partitioned table must be part ...
https://dev.mysql.com/doc/refman/8.0/en/privileges-provided.html
AUDIT_ABORT_EXEMPT (added in MySQL 8.0.28) Allows queries blocked by an “abort” item in the audit log filter. SKIP_QUERY_REWRITE (added in MySQL 8.0.31) Queries issued by a user with this privilege are not subject to being rewritten by the ...
https://dev.mysql.com/doc/refman/8.0/en/replication-options-source.html
This section describes the server options and system variables that you can use on replication source servers. You can specify the options either on the command line or in an option file. On the source and each replica, you must set the server_id ...
https://dev.mysql.com/doc/refman/8.0/en/stored-objects-security.html
If the account you are searching for does not exist, any objects displayed by those queries are orphan objects. Stored programs (procedures, functions, triggers, and events) and views are defined prior to use and, when referenced, execute within a ...
https://dev.mysql.com/doc/refman/8.0/en/where-optimization.html
You might be tempted to rewrite your queries to make arithmetic operations faster, while sacrificing readability. Each table index is queried, and the best index is used unless the optimizer believes that it is more efficient to use a table scan.
https://dev.mysql.com/doc/refman/8.0/en/counting-rows.html
Counting the total number of animals you have is the same question as “How many rows are in the pet table?” because there is one record per pet. COUNT(*) counts the number of rows, so the query to count your animals looks like this: mysql> ...
https://dev.mysql.com/doc/refman/8.0/en/engine-condition-pushdown-optimization.html
This has the potential to improve performance of queries by a significant margin. This optimization improves the efficiency of direct comparisons between a nonindexed column and a constant. In such cases, the condition is “pushed down” to the ...
https://dev.mysql.com/doc/refman/8.0/en/function-optimization.html
A function is nondeterministic if, given fixed values for its arguments, it can return different results for different invocations. If a function is tagged nondeterministic, a reference to it in a WHERE clause is evaluated for every row (when ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-consistent-read.html
You can get a fresher snapshot for your queries by committing the current transaction and after that issuing new queries. A consistent read means that InnoDB uses multi-versioning to present to a query a snapshot of the database at a point in time.