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https://dev.mysql.com/doc/refman/8.4/en/limit-optimization.html
If you need only a specified number of rows from a result set, use a LIMIT clause in the query, rather than fetching the whole result set and throwing away the extra data. MySQL sometimes optimizes a query that has a LIMIT row_count clause and no ...If ordering is done by using an index, this is very ...
https://dev.mysql.com/doc/refman/8.4/en/update.html
To avoid this problem, add an ORDER BY clause to cause the rows with larger id values to be updated before those with smaller values: UPDATE t SET id = id + 1 ORDER BY id DESC; You can also perform UPDATE operations covering multiple tables. UPDATE ...An UPDATE statement can start with a WITH clause to define common table expressions accessible within the ...
https://dev.mysql.com/doc/extending-mysql/8.4/en/adding-loadable-function.html
You can define simple functions that operate on a single row at a time, or aggregate functions that operate on groups of rows. Otherwise, MySQL calls the main function xxx() once for each row. After all rows have been processed, MySQL calls the ...
https://dev.mysql.com/doc/x-devapi-userguide/en/using-sql.html
In addition to the simplified X DevAPI syntax of the Session object, the Session object has a sql() function that takes any SQL statement as a string. The following example uses a Session to call an SQL Stored Procedure on the specific node.
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndb-api-statistics.html
Ndb_api_pruned_scan_count_session Ndb_api_pruned_scan_count_replica [none] Ndb_api_pruned_scan_count ScanBatchCount Number of batches of rows received. (A batch in this context is a set of scan results from a single fragment.) ... A number of types ...
https://dev.mysql.com/doc/ndbapi/en/overview-operations.html
1.4.2.3.2 Single-row operations After the operation is created using NdbTransaction::getNdbOperation() or NdbTransaction::getNdbIndexOperation(), it is defined in the following three steps: Specify the standard operation type using ... An ...
https://dev.mysql.com/doc/refman/8.4/en/create-table-secondary-indexes.html
Even with additional write costs, secondary indexes on virtual columns may be preferable to generated stored columns, which are materialized in the clustered index, resulting in larger tables that require more disk space and memory. If a secondary ...A secondary index defined on a virtual column is sometimes referred to as a “virtual ...
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-online-operations.html
Reads rows from the original table, and writes them to the copy. Other NDB clients can modify row data during a copying ALTER TABLE, resulting in inconsistency. row *************************** Level: Warning Code: 1478 Message: DYNAMIC column c4 ...
https://dev.mysql.com/doc/refman/8.4/en/subquery-optimization-with-exists.html
WHERE subquery_where) MySQL evaluates queries “from outside to inside.” That is, it first obtains the value of the outer expression outer_expr, and then runs the subquery and captures the rows that it produces. A very useful optimization is to ... Certain optimizations are applicable to comparisons that use the IN (or =ANY) operator to test subquery ...
https://dev.mysql.com/doc/refman/8.4/en/comparison-operators.html
The following relational comparison operators can be used to compare not only scalar operands, but row operands: = > < >= <= <> != The descriptions for those operators later in this section detail how they work with row operands. For additional ...