See Also API, Connector/J, J2EE, Java. 

## JNDI 

See Also Java. 

## join 

 A query  that retrieves data from more than one table, by referencing columns in the tables that hold identical values. Ideally, these columns are part of an InnoDB foreign key  relationship, which ensures referential integrity  and that the join columns are indexed . Often used to save space and improve query performance by replacing repeated strings with numeric IDs, in a normalized  data design. See Also foreign key, index, normalized, query, referential integrity. 

## K 

## keystore 

See Also SSL. 

## KEY_BLOCK_SIZE 

 An option to specify the size of data pages within an InnoDB  table that uses compressed row format . The default is 8 kilobytes. Lower values risk hitting internal limits that depend on the combination of row size and compression percentage. 

For MyISAM  tables, KEY_BLOCK_SIZE  optionally specifies the size in bytes to use for index key blocks. The value is treated as a hint; a different size could be used if necessary. A KEY_BLOCK_SIZE  value specified for an individual index definition overrides a table-level KEY_BLOCK_SIZE  value. See Also compressed row format. 

## L 

## latch 

 A lightweight structure used by InnoDB  to implement a lock  for its own internal memory structures, typically held for a brief time measured in milliseconds or microseconds. A general term that includes both mutexes  (for exclusive access) and rw-locks  (for shared access). Certain latches are the focus of InnoDB  performance tuning. Statistics about latch use and contention are available through the Performance Schema  interface. See Also lock, locking, mutex, Performance Schema, rw-lock. 

## libmysql 

 Informal name for the libmysqlclient  library. See Also libmysqlclient. 

## libmysqlclient 

 The library file, named libmysqlclient.a  or libmysqlclient.so , that is typically linked into client programs written in C . Sometimes known informally as libmysql  or the mysqlclient  library. See Also client, libmysql, mysqlclient. 

## libmysqld 

 This embedded  MySQL server library makes it possible to run a full-featured MySQL server inside a client application. The main benefits are increased speed and more simple management for embedded applications. You link with the libmysqld  library rather than libmysqlclient . The API is identical between all three of these libraries. 

See Also client, embedded, libmysql, libmysqlclient. 

