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https://dev.mysql.com/doc/refman/8.4/en/index-extensions.html
EXPLAIN for the query produces this result: mysql> EXPLAIN SELECT COUNT(*) FROM t1 WHERE i1 = 3 AND d = '2000-01-01'\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: t1 type: ref possible_keys: ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-processlist-table.html
DB The default database for the thread, or NULL if none has been selected. For example, if a CALL statement executes a stored procedure that is executing a SELECT statement, the INFO value shows the SELECT statement. The following statements are ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-tables-table.html
In such cases, use SELECT COUNT(*) to obtain an accurate count. A more accurate method of obtaining this information in such cases is to query the INFORMATION_SCHEMA PARTITIONS table, as shown in this example: SELECT SUM(DATA_FREE) FROM ...The ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlocks-handling.html
Use EXPLAIN SELECT to determine which indexes the MySQL server regards as the most appropriate for your queries. If you can afford to permit a SELECT to return data from an old snapshot, do not add a FOR UPDATE or FOR SHARE clause to it. This ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-fulltext-index.html
mysql> SELECT index_id, name, table_id, space from INFORMATION_SCHEMA.INNODB_INDEXES WHERE index_id=457; +----------+------+----------+-------+ | index_id | name | table_id | space | +----------+------+----------+-------+ | 457 | idx | 327 | 283 | ... Full-text indexes are created on text-based columns (CHAR, VARCHAR, or TEXT columns) to speed up queries and DML operations on data contained within those ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-information-schema-files-table.html
mysql> SELECT FILE_ID, FILE_NAME, FILE_TYPE, TABLESPACE_NAME, FREE_EXTENTS, -> TOTAL_EXTENTS, EXTENT_SIZE, INITIAL_SIZE, MAXIMUM_SIZE, AUTOEXTEND_SIZE, DATA_FREE, STATUS ENGINE -> FROM INFORMATION_SCHEMA.FILES WHERE TABLESPACE_NAME LIKE ... The ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-next-key-locking.html
For example, if a SELECT is executed twice, but returns a row the second time that was not returned the first time, the row is a “phantom” row. If you were to execute the same SELECT within the same transaction, you would see a new row with an ... The so-called phantom problem occurs within a transaction when the same query produces different sets of rows at different ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-performance-ro-txn.html
A transaction ID is only needed for a transaction that might perform write operations or locking reads such as SELECT ... The autocommit setting is turned on, so that the transaction is guaranteed to be a single statement, and the single statement ... InnoDB can avoid the overhead associated with setting up the transaction ID (TRX_ID field) for transactions that are known to be ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-row-format.html
mysql> SELECT @@innodb_default_row_format; +-----------------------------+ | @@innodb_default_row_format | +-----------------------------+ | dynamic | +-----------------------------+ mysql> CREATE TABLE t1 (c1 INT); mysql> SELECT * FROM ... The row ...
https://dev.mysql.com/doc/refman/8.4/en/json-creation-functions.html
mysql> SELECT JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()); +---------------------------------------------+ | JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()) | +---------------------------------------------+ | [1, "abc", null, true, "11:30:24.000000"] | ... The functions listed in this section compose JSON values from component ...