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https://dev.mysql.com/doc/refman/8.0/en/alter-table.html
If an ALTER TABLE operation on a multicolumn index used to partition a table by KEY changes the order of the columns, it can only be performed using ALGORITHM=COPY. Renaming, Redefining, and Reordering Columns The CHANGE, MODIFY, RENAME COLUMN, and ... ALTER TABLE tbl_name [alter_option [, alter_option] ...] [partition_options] alter_option: { table_options | ADD [COLUMN] col_name column_definition [FIRST | AFTER col_name] | ADD [COLUMN] (col_name column_definition,...) | ADD {INDEX | KEY} [index_name] [index_type] (key_part,...) [index_option] ...
https://dev.mysql.com/doc/refman/8.0/en/group-by-handling.html
SQL-92 and earlier does not permit queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are not named in the GROUP BY clause. If the ONLY_FULL_GROUP_BY SQL mode is enabled (which it is by ...
https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html
Disabling foreign key checking can be useful for reloading InnoDB tables in an order different from that required by their parent/child relationships. Component order is significant because the server executes components in the order listed. The ...
https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html
For details on the rules for conversion of values between JSON and other types, see Comparison and Ordering of JSON Values. Casting between spatial types does not change coordinate values or order. If the expression to cast is a well-formed geometry ... Table 14.15 Cast Functions and Operators Name Description Deprecated BINARY Cast a string to a binary string 8.0.27 CAST() Cast a value as a certain type CONVERT() Cast a value as a certain type Cast functions and operators enable conversion of values from one data type to ...
https://dev.mysql.com/doc/refman/8.0/en/problems-with-float.html
Floating-point numbers sometimes cause confusion because they are approximate and not stored as exact values. A floating-point value as written in an SQL statement may not be the same as the value represented internally. Attempts to treat ...
https://dev.mysql.com/doc/refman/8.0/en/group-by-modifiers.html
Previously, MySQL did not allow the use of DISTINCT or ORDER BY in a query having a WITH ROLLUP option. WITH ROLLUP queries, to test whether NULL values in the result represent super-aggregate values, the GROUPING() function is available for use in ... The GROUP BY clause permits a WITH ROLLUP modifier that causes summary output to include extra rows that represent higher-level (that is, super-aggregate) summary ...
https://dev.mysql.com/doc/refman/8.0/en/tracing-example.html
row *************************** QUERY: SELECT SUM(alias2.col_varchar_nokey) AS c1, alias2.pk AS c2 FROM t1 AS alias1 STRAIGHT_JOIN t2 AS alias2 ON alias2.pk = alias1.col_int_key WHERE alias1.pk GROUP BY c2 ORDER BY alias1.col_int_key, alias2.pk This ...Now we can examine the trace, whose first column (QUERY), containing the original statement to be traced, is shown here: SELECT * FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE\G ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-replication-conflict-resolution.html
The epoch-based conflict resolution functions NDB$EPOCH() and NDB$EPOCH_TRANS() compare the order in which epochs are replicated (and thus these functions are transactional). The NDB$EPOCH() and NDB$EPOCH_TRANS() functions discussed later in this ...
https://dev.mysql.com/doc/refman/8.0/en/update.html
Single-table syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_reference SET assignment_list [WHERE where_condition] [ORDER BY ...] [LIMIT row_count] value: {expr | DEFAULT} assignment: col_name = value assignment_list: assignment [, assignment] ... If ... UPDATE is a DML statement that modifies rows in a ...
https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html
MySQL supports descending indexes: DESC in an index definition is no longer ignored but causes storage of key values in descending order. Previously, indexes could be scanned in reverse order but at a performance penalty. A descending index can be ...For InnoDB full-text search, this means that the index required on the FTS_DOC_ID column of the indexed table cannot be defined as a descending ...