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https://dev.mysql.com/doc/refman/5.7/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 ...
https://dev.mysql.com/doc/refman/5.7/en/json-function-reference.html
Table 12.22 JSON Functions Name Description Introduced Deprecated -> Return value from JSON column after evaluating path; equivalent to JSON_EXTRACT(). ->> Return value from JSON column after evaluating path and unquoting the result; equivalent to ...
https://dev.mysql.com/doc/refman/5.7/en/limit-optimization.html
In this case, as we can see from the EXPLAIN output, it uses the table's primary key. row *************************** id: 1 select_type: SIMPLE table: t partitions: NULL type: range possible_keys: i key: i key_len: 8 ref: NULL rows: 14 filtered: ...
https://dev.mysql.com/doc/refman/5.7/en/merge-storage-engine.html
There it is indexed but not as a PRIMARY KEY because a MERGE table cannot enforce uniqueness over the set of underlying tables. The MERGE storage engine, also known as the MRG_MyISAM engine, is a collection of identical MyISAM tables that can be ...
https://dev.mysql.com/doc/refman/5.7/en/myisampack.html
When the table is used later, the server reads into memory the information needed to decompress columns. This results in much better performance when accessing individual rows, because you only have to uncompress exactly one row. MySQL uses mmap() ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-limitations-unsupported.html
A number of features supported by other storage engines are not supported for NDB tables. Trying to use any of these features in NDB Cluster does not cause errors in or of itself; however, errors may occur in applications that expects the features ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-counters.html
A primary-key read counts as one operation, as does a primary-key update. LOCAL_WRITES and LOCAL_READS are primary-key operations using a transaction coordinator in a node that also holds the primary fragment replica of the record. The counters ...
https://dev.mysql.com/doc/refman/5.7/en/nested-loop-joins.html
MySQL join buffering has these characteristics: Join buffering can be used when the join is of type ALL or index (in other words, when no possible keys can be used, and a full scan is done, of either the data or index rows, respectively), or range.
https://dev.mysql.com/doc/refman/5.7/en/optimizer-hints.html
The parser recognizes optimizer hint comments after the initial keyword of SELECT, UPDATE, INSERT, REPLACE, and DELETE statements. Table-Level Optimizer Hints Table-level hints affect use of the Block Nested-Loop (BNL) and Batched Key Access (BKA) ... One means of control over optimizer strategies is to set the optimizer_switch system variable (see Section 8.9.2, “Switchable ...
https://dev.mysql.com/doc/refman/5.7/en/optimizer-issues.html
To use it, just add the keyword EXPLAIN to the front of your SELECT statement: mysql> EXPLAIN SELECT * FROM t1, t2 WHERE t1.i = t2.i; EXPLAIN is discussed in more detail in Section 13.8.2, “EXPLAIN Statement”. Use ANALYZE TABLE tbl_name to ...