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https://dev.mysql.com/doc/refman/8.0/en/nested-join-optimization.html
In some of the following examples, NULL where a table name appears means a row in which NULL is used for each column of that table. For example, t1||t2||NULL indicates a row constructed by concatenating the columns of rows t1 and t2, and NULL for ...
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/create-table.html
NOT NULL | NULL If neither NULL nor NOT NULL is specified, the column is treated as though NULL had been specified. In MySQL 8.0, only the InnoDB, MyISAM, and MEMORY storage engines support indexes on columns that can have NULL values. In other ...| ...
https://dev.mysql.com/doc/refman/8.0/en/derived-tables.html
row *************************** id: 1 select_type: PRIMARY table: <derived2> partitions: NULL type: system possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 1 filtered: 100.00 Extra: NULL *************************** 2. row ...For ...
https://dev.mysql.com/doc/refman/8.0/en/glossary.html
It provides useful information for the query optimizer, because the column is known to be not null and with unique values. A column can be subject to a unique constraint, a NOT NULL constraint, or both. See Also cardinality, foreign key, index, NOT ... These terms are commonly used in information about the MySQL database ...
https://dev.mysql.com/doc/refman/8.0/en/partitioning-range.html
A table that is partitioned by range is partitioned in such a way that each partition contains rows for which the partitioning expression value lies within a given range. Ranges should be contiguous but not overlapping, and are defined using the ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization-with-exists.html
This section discusses these optimizations, particularly with regard to the challenges that NULL values present. The “pushdown” strategy just described works if either of these conditions is true: outer_expr and inner_expr cannot be NULL.
https://dev.mysql.com/doc/refman/8.0/en/json.html
Prior to MySQL 8.0.13, a JSON column cannot have a non-NULL default value. A path that does not exist in the document (evaluates to nonexistent data) evaluates to NULL. $[3] evaluates to NULL (it refers to the fourth array element, which does not ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-programs-ndb-desc.html
ndb_desc provides a detailed description of one or more NDB tables. Usage ndb_desc -c connection_string tbl_name -d db_name [options] ndb_desc -c connection_string index_name -d db_name -t tbl_name Additional options that can be used with ndb_desc ...
https://dev.mysql.com/doc/refman/8.0/en/bit-functions.html
The result type depends on whether the arguments are evaluated as binary strings or numbers: Binary-string evaluation occurs when the arguments have a binary string type, and at least one of them is not a hexadecimal literal, bit literal, or NULL ...