写了一个简单的工具类，获取数据库的表、表中字段、字段类型、字段注释等信息。代码如下：
package com.lnjecit.generator.util;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class DatabaseUtil {
private final static Logger LOGGER = LoggerFactory.getLogger(DatabaseUtil.class);
private static final String DRIVER = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://localhost:3306/javaweb?useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
private static final String USERNAME = "root";
private static final String PASSWORD = "mysql";
private static final String SQL = "SELECT * FROM ";// 数据库操作
static {
try {
Class.forName(DRIVER);
} catch (ClassNotFoundException e) {
LOGGER.error("can not load jdbc driver", e);
}
}
/**
* 获取数据库连接
*
* @return
*/
public static Connection getConnection() {
Connection conn = null;
try {
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
} catch (SQLException e) {
LOGGER.error("get connection failure", e);
}
return conn;
}
/**
* 关闭数据库连接
* @param conn
*/
public static void closeConnection(Connection conn) {
if(conn != null) {
try {
conn.close();
} catch (SQLException e) {
LOGGER.error("close connection failure", e);
}
}
}
/**
* 获取数据库下的所有表名
*/
public static List<String> getTableNames() {
List<String> tableNames = new ArrayList<>();
Connection conn = getConnection();
ResultSet rs = null;
try {
//获取数据库的元数据
DatabaseMetaData db = conn.getMetaData();
System.out.println("conn.getCatalog() = " + conn.getCatalog());
//从元数据中获取到所有的表名
rs = db.getTables(conn.getCatalog(), null, null, new String[] { "TABLE" });
while(rs.next()) {
String tableName = (String) rs.getObject("TABLE_NAME");
System.out.println("tableName:" + tableName);
tableNames.add(rs.getString(3));
}
} catch (SQLException e) {
LOGGER.error("getTableNames failure", e);
} finally {
try {
rs.close();
closeConnection(conn);
} catch (SQLException e) {
LOGGER.error("close ResultSet failure", e);
}
}
return tableNames;
}
/**
* 获取表中所有字段名称
* @param tableName 表名
* @return
*/
public static List<String> getColumnNames(String tableName) {
List<String> columnNames = new ArrayList<>();
//与数据库的连接
Connection conn = getConnection();
PreparedStatement pStemt = null;
String tableSql = SQL + tableName;
try {
pStemt = conn.prepareStatement(tableSql);
//结果集元数据
ResultSetMetaData rsmd = pStemt.getMetaData();
//表列数
int size = rsmd.getColumnCount();
for (int i = 0; i < size; i++) {
columnNames.add(rsmd.getColumnName(i + 1));
}
} catch (SQLException e) {
LOGGER.error("getColumnNames failure", e);
} finally {
if (pStemt != null) {
try {
pStemt.close();
closeConnection(conn);
} catch (SQLException e) {
LOGGER.error("getColumnNames close pstem and connection failure", e);
}
}
}
return columnNames;
}
/**
* 获取表中所有字段类型
* @param tableName
* @return
*/
public static List<String> getColumnTypes(String tableName) {
List<String> columnTypes = new ArrayList<>();
//与数据库的连接
Connection conn = getConnection();
PreparedStatement pStemt = null;
String tableSql = SQL + tableName;
try {
pStemt = conn.prepareStatement(tableSql);
//结果集元数据
ResultSetMetaData rsmd = pStemt.getMetaData();
//表列数
int size = rsmd.getColumnCount();
for (int i = 0; i < size; i++) {
columnTypes.add(rsmd.getColumnTypeName(i + 1));
}
} catch (SQLException e) {
LOGGER.error("getColumnTypes failure", e);
} finally {
if (pStemt != null) {
try {
pStemt.close();
closeConnection(conn);
} catch (SQLException e) {
LOGGER.error("getColumnTypes close pstem and connection failure", e);
}
}
}
return columnTypes;
}
/**
* 获取表中字段的所有注释
* @param tableName
* @return
*/
public static List<String> getColumnComments(String tableName) {
List<String> columnTypes = new ArrayList<>();
//与数据库的连接
Connection conn = getConnection();
PreparedStatement pStemt = null;
String tableSql = SQL + tableName;
List<String> columnComments = new ArrayList<>();//列名注释集合
ResultSet rs = null;
try {
pStemt = conn.prepareStatement(tableSql);
rs = pStemt.executeQuery("show full columns from " + tableName);
while (rs.next()) {
columnComments.add(rs.getString("Comment"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs.close();
closeConnection(conn);
} catch (SQLException e) {
LOGGER.error("getColumnComments close ResultSet and connection failure", e);
}
}
}
return columnComments;
}
public static void main(String[] args) {
List<String> tableNames = getTableNames();
System.out.println("tableNames:" + tableNames);
for (String tableName : tableNames) {
System.out.println("ColumnNames:" + getColumnNames(tableName));
System.out.println("ColumnTypes:" + getColumnTypes(tableName));
System.out.println("ColumnComments:" + getColumnComments(tableName));
}
}
}运行代码之前，先将数据库配置进行修改，再运行代码就可以获取数据库表的详细结构了。
获取MySQL数据库表结构的信息（字段名，字段类型，注释等）_select column_name,data_type,column_comment-CSDN博客
直接复制查询用就懂了！！
select COLUMN_NAME,DATA_TYPE,COLUMN_COMMENT from information_schema.columns where TABLE_NAME='表名'或者
select COLUMN_NAME,DATA_TYPE,COLUMN_COMMENT from information_schema.COLUMNS where table_name = '表名' and table_schema = '数据库名称';或者
SHOW FULL COLUMNS FROM 表名information_schema.columns：MySQL的information_schema库中有个COLUMNS表，里面记录了mysql所有库中所有表的字段信息，该表信息如下
COLUMN_NAME：字段名
DATA_TYPE：数据类型
COLUMN_COMMENT ：注释
大佬有话说：
- MySQL中表的字段信息查询--information_schema.COLUMNS_lkforce的博客-CSDN博客_mysql获取表字段信息
- Sql中获取表结构（字段名称，类型，长度，说明） - InDulGed - 博客园
- 4.2.2 查看表结构 SHOW COLUMNS 或DESCRIBE_Simon@的博客-CSDN博客_describe语句查看表
-
SHOW FULL COLUMNS FROM 表名 //获取表结构的所有信息（含注释）
-
-
SHOW COLUMNS FROM 表名 //获取表结构的信息
-
-
DESCRIBE 数据表名 //获取表结构的信息( 其中DESCRIBE 可已简写成DESC)
-
-
DESCRIBE 数据表名 列名 //获取表结构某一列的信息
-
-
SHOW INDEX FROM <表名> //查看表索引
MySQL 中information_schema、mysql、performance_schema、sys 简介
一、information_schema简介
在MySQL中，把 information_schema 看作是一个数据库，确切说是信息数据库。其中保存着关于MySQL服务器所维护的所有其他数据库的信息。如数据库名，数据库的表，表栏的数据类型与访问权 限等。在INFORMATION_SCHEMA中，有数个只读表。它们实际上是视图，而不是基本表，因此，你将无法看到与之相关的任何文件。
information_schema数据库表说明:![复制代码]()
1 1、SCHEMATA表：提供了当前mysql实例中所有数据库的信息。是show databases的结果取之此表。 2 3 2、TABLES表：提供了关于数据库中的表的信息（包括视图）。详细表述了某个表属于哪个schema，表类型，表引擎，创建时间等信息。是show tables from schemaname的结果取之此表。 4 5 3、COLUMNS表：提供了表中的列信息。详细表述了某张表的所有列以及每个列的信息。是show columns from schemaname.tablename的结果取之此表。 6 7 4、STATISTICS表：提供了关于表索引的信息。是show index from schemaname.tablename的结果取之此表。 8 9 5、USER_PRIVILEGES（用户权限）表：给出了关于全程权限的信息。该信息源自mysql.user授权表。是非标准表。 10 11 6、SCHEMA_PRIVILEGES（方案权限）表：给出了关于方案（数据库）权限的信息。该信息来自mysql.db授权表。是非标准表。 12 13 7、TABLE_PRIVILEGES（表权限）表：给出了关于表权限的信息。该信息源自mysql.tables_priv授权表。是非标准表。 14 15 8、COLUMN_PRIVILEGES（列权限）表：给出了关于列权限的信息。该信息源自mysql.columns_priv授权表。是非标准表。 16 17 9、CHARACTER_SETS（字符集）表：提供了mysql实例可用字符集的信息。是SHOW CHARACTER SET结果集取之此表。 18 19 10、COLLATIONS表：提供了关于各字符集的对照信息。 20 21 11、COLLATION_CHARACTER_SET_APPLICABILITY表：指明了可用于校对的字符集。这些列等效于SHOW COLLATION的前两个显示字段。 22 23 12、TABLE_CONSTRAINTS表：描述了存在约束的表。以及表的约束类型。 24 25 13、KEY_COLUMN_USAGE表：描述了具有约束的键列。 26 27 14、ROUTINES表：提供了关于存储子程序（存储程序和函数）的信息。此时，ROUTINES表不包含自定义函数（UDF）。名为“mysql.proc name”的列指明了对应于INFORMATION_SCHEMA.ROUTINES表的mysql.proc表列。 28 29 15、VIEWS表：给出了关于数据库中的视图的信息。需要有show views权限，否则无法查看视图信息。 30 31 16、TRIGGERS表：提供了关于触发程序的信息。必须有super权限才能查看该表
查看引擎
information_schema.ENGINS 对应于 show engines;查看数据库
information_schema.SCHEMATA 对应于 show databases;查看表
information_schema.TABLES 对应于 show tables;查看列
information_schema.COLUMNS 对应于show columns from table_name查看索引
information_schema.STATISTICS 对应于show index from table_name
查看线程
information_schema.PROCESSLIST 对应于 show processlist![复制代码]()
二.MySQL 库表简介
![复制代码]()
在mysql数据库中，有mysql_install_db脚本初始化权限表，存储权限的表有： 1、user表: 用户列、权限列、安全列、资源控制列 2、db表 : 用户列、权限列 3、host表 4、table_priv表 5、columns_priv表 6、proc_priv表
![复制代码]()
三.sys库表简介
![复制代码]()
sys_config ： 这是在这个系统库上存在的唯一一个表了, 表结构如下： CREATE TABLE `sys_config` ( `variable` varchar(128) NOT NULL, `value` varchar(128) DEFAULT NULL, `set_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, `set_by` varchar(128) DEFAULT NULL, PRIMARY KEY (`variable`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 • variable ： 配置选项名称 • value ： 配置选项值 • set_time： 该行配置修改的时间 • set_by ： 该行配置信息修改者，如果从被安装没有修改过，那么这个数据应该为NULL 这里写图片描述 以上值的会话变量为@sys.+表中variable字段，譬如：@sys.statement_truncate_len 可以set @sys.statement_truncate_len = 32 临时改变值，在会话中会一直使用这个值，如果想要恢复使用表的默认值，只需要将这个会话值设置为null；set @sys.statement_truncate_len = null; • diagnostics.allow_i_s_tables : 默认为OFF ，如果开启表示允许diagnostics() 存储过程执行扫描information_schema.tables 表，如果表很多，那么可能会很耗性能， • diagnostics.include_raw : 默认为OFF ， 开启将会从metrics 视图输出未加工处理的数据 。 • statement_performance_analyzer.limit : 视图在没有加limit限制时，返回的最大行数 • statement_performance_analyzer.view • statement_truncate_len : 通过format_statement()函数返回值的最大长度 这个表非默认选项还有一个@sys.debug参数 , 可以手动加入: INSERT INTO sys_config (variable, value) VALUES('debug', 'ON'); UPDATE sys_config SET value = 'OFF' WHERE variable = 'debug'; SET @sys.debug = NULL;![复制代码]()
四.performance_schema库表简介
![复制代码]()
1 performance_schema是运行在较低级别的用于监控MySQL Server运行过程中的资源消耗、资源等待等情况的一个功能特性，也是一个存储引擎。该特性具有以下特点。 2 3 提供了一种在数据库运行时实时检查Server内部执行情况的方法 4 可监控任何事情以及对应的时间消耗，利用这些信息来判断Server中的相关资源消耗 5 只被记录在本地Server的performance_schema中，其表中数据发生变化时不会被写入binlog中，也不会通过复制机制被复制到其他Server中 6 对于这些表可使用SELECT语句查询，也可以使用SQL语句更新performance_schema数据库中的表记录，但不建议更新，会影响后续的数据收集 7 表中数据不会持久化存储在磁盘中，而是保存在内存中，一旦服务器重启，这些数据就会丢失 8 不会导致server的行为发生变化（查询，优化等） 9 总体上开销有限也不会影响性能 10 对某事件监测失败，不影响server正常运行 11 当针对一个数据，同时被performance_schema收集和查询，则收集优先与查询 12 事件监测点可进行配置
![复制代码]()
- 查看是否当前数据库是否支持
![复制代码]()
mysql> sho engines; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'sho engines' at line 1 mysql> show engines; +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine | Support | Comment | Transactions | XA | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL | | MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES | | PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO | | MyISAM | YES | MyISAM storage engine | NO | NO | NO | | MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO | | BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO | | CSV | YES | CSV storage engine | NO | NO | NO | | ARCHIVE | YES | Archive storage engine | NO | NO | NO | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ 9 rows in set (0.00 sec)
Support 为YES 表示支持![复制代码]()
- 查看该特性是否使能
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![复制代码]()
1 mysql> show variables like 'performance_schema'; 2 +--------------------+-------+ 3 | Variable_name | Value | 4 +--------------------+-------+ 5 | performance_schema | ON | 6 +--------------------+-------+ 7 1 row in set (0.00 sec)
如果为off则表示未使能。该参数为只读参数，则可在mysql.cnf中进行配置后重启服务![复制代码]()
使用该引擎的这些表的分类
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1）语句事件记录表 mysql> show tables like 'events_statement%'; +----------------------------------------------------+ | Tables_in_performance_schema (events_statement%) | +----------------------------------------------------+ | events_statements_current | //当前语句事件表 | events_statements_histogram_by_digest | //历史语句事件表 | events_statements_histogram_global | | events_statements_history | | events_statements_history_long | //长语句历史事件表 | events_statements_summary_by_account_by_event_name | //聚合后的摘要表 | events_statements_summary_by_digest | | events_statements_summary_by_host_by_event_name | | events_statements_summary_by_program | | events_statements_summary_by_thread_by_event_name | | events_statements_summary_by_user_by_event_name | | events_statements_summary_global_by_event_name | +----------------------------------------------------+ 12 rows in set (0.00 sec) 2）等待时间记录表 mysql> show tables like 'events_wait%'; +-----------------------------------------------+ | Tables_in_performance_schema (events_wait%) | +-----------------------------------------------+ | events_waits_current | | events_waits_history | | events_waits_history_long | | events_waits_summary_by_account_by_event_name | | events_waits_summary_by_host_by_event_name | | events_waits_summary_by_instance | | events_waits_summary_by_thread_by_event_name | | events_waits_summary_by_user_by_event_name | | events_waits_summary_global_by_event_name | +-----------------------------------------------+ 9 rows in set (0.00 sec) 3）阶段事件记录表 mysql> show tables like 'events_stage%'; +------------------------------------------------+ | Tables_in_performance_schema (events_stage%) | +------------------------------------------------+ | events_stages_current | | events_stages_history | | events_stages_history_long | | events_stages_summary_by_account_by_event_name | | events_stages_summary_by_host_by_event_name | | events_stages_summary_by_thread_by_event_name | | events_stages_summary_by_user_by_event_name | | events_stages_summary_global_by_event_name | +------------------------------------------------+ 8 rows in set (0.00 sec) 4）事务事件记录表 mysql> show tables like 'events_transaction%'; +------------------------------------------------------+ | Tables_in_performance_schema (events_transaction%) | +------------------------------------------------------+ | events_transactions_current | | events_transactions_history | | events_transactions_history_long | | events_transactions_summary_by_account_by_event_name | | events_transactions_summary_by_host_by_event_name | | events_transactions_summary_by_thread_by_event_name | | events_transactions_summary_by_user_by_event_name | | events_transactions_summary_global_by_event_name | +------------------------------------------------------+ 8 rows in set (0.00 sec) 5）监控文件系统层调用的表 mysql> show tables like '%file%'; +---------------------------------------+ | Tables_in_performance_schema (%file%) | +---------------------------------------+ | file_instances | | file_summary_by_event_name | | file_summary_by_instance | +---------------------------------------+ 3 rows in set (0.00 sec) 6）监视内存使用的表 mysql> show tables like '%memory%'; +-----------------------------------------+ | Tables_in_performance_schema (%memory%) | +-----------------------------------------+ | memory_summary_by_account_by_event_name | | memory_summary_by_host_by_event_name | | memory_summary_by_thread_by_event_name | | memory_summary_by_user_by_event_name | | memory_summary_global_by_event_name | +-----------------------------------------+ 5 rows in set (0.00 sec) 7）动态对performance_schema进行配置的配置表 mysql> show tables like '%setup%'; +----------------------------------------+ | Tables_in_performance_schema (%setup%) | +----------------------------------------+ | setup_actors | | setup_consumers | | setup_instruments | | setup_objects | | setup_threads | +----------------------------------------+ 5 rows in set (0.01 sec)
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查询性能表进行进行分析
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两个基本概念 ● instruments：生产者，用于采集MySQL中各种操作产生的事件信息，对应配置表中的配置项，我们可以称之为事件采集配置项。以下提及的生产者均统称为instruments。 ● consumers：消费者，对应的消费者表用于存储来自instruments采集的数据，对应配置表中的配置项，我们可以称之为消费存储配置项。以下提及的消费者均统称为consumers。 1、哪类的SQL执行最多？ mysql> SELECT DIGEST_TEXT,COUNT_STAR,FIRST_SEEN,LAST_SEEN FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC -> ; +----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+ | DIGEST_TEXT | COUNT_STAR | FIRST_SEEN | LAST_SEEN | +----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+ | SHOW VARIABLES LIKE ? | 4 | 2022-01-04 18:14:24.153156 | 2022-01-04 21:25:12.396097 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 3 | 2022-01-04 18:06:55.067124 | 2022-01-04 18:21:09.809550 | 2、哪类SQL的平均响应时间最多？ mysql> SELECT DIGEST_TEXT,AVG_TIMER_WAIT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC ; +----------------------------------------------------------------------------------------------------------------------------------------+----------------+ | DIGEST_TEXT | AVG_TIMER_WAIT | +----------------------------------------------------------------------------------------------------------------------------------------+----------------+ | SHOW VARIABLES LIKE ? | 5867400000 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 42246300000 | 3、哪类SQL排序记录数最多？ mysql> SELECT DIGEST_TEXT,SUM_SORT_ROWS FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+---------------+ | DIGEST_TEXT | SUM_SORT_ROWS | +----------------------------------------------------------------------------------------------------------------------------------------+---------------+ | SHOW VARIABLES LIKE ? | 0 | 4、哪类SQL扫描记录数最多？ mysql> SELECT DIGEST_TEXT,SUM_ROWS_EXAMINED FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+-------------------+ | DIGEST_TEXT | SUM_ROWS_EXAMINED | +----------------------------------------------------------------------------------------------------------------------------------------+-------------------+ | SHOW VARIABLES LIKE ? | 51 | 5、哪类SQL使用临时表最多？ mysql> SELECT DIGEST_TEXT,SUM_CREATED_TMP_TABLES,SUM_CREATED_TMP_DISK_TABLES FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+ | DIGEST_TEXT | SUM_CREATED_TMP_TABLES | SUM_CREATED_TMP_DISK_TABLES | +----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+ | SHOW VARIABLES LIKE ? | 4 | 0 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 0 | 0 | 6、哪类SQL返回结果集最多？ mysql> SELECT DIGEST_TEXT,SUM_ROWS_SENT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC; +-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+ | DIGEST_TEXT | SUM_ROWS_SENT | +-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+ | SHOW VARIABLES LIKE ? | 51 | | SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 38 | 7、哪个表物理IO最多？ mysql> SELECT file_name,event_name,SUM_NUMBER_OF_BYTES_READ,SUM_NUMBER_OF_BYTES_WRITE FROM file_summary_by_instance ORDER BY SUM_NUMBER_OF_BYTES_READ + SUM_NUMBER_OF_BYTES_WRITE DESC; +------------------------------------------+---------------------------------------+--------------------------+---------------------------+ | file_name | event_name | SUM_NUMBER_OF_BYTES_READ | SUM_NUMBER_OF_BYTES_WRITE | +------------------------------------------+---------------------------------------+--------------------------+---------------------------+ | /var/lib/mysql/ibtmp1 | wait/io/file/innodb/innodb_data_file | 0 | 14729216 | | /var/lib/mysql/#ib_16384_1.dblwr | wait/io/file/innodb/innodb_dblwr_file | 8585216 | 0 | 8、哪个表逻辑IO最多？ mysql> SELECT object_name,COUNT_READ,COUNT_WRITE,COUNT_FETCH,SUM_TIMER_WAIT FROM table_io_waits_summary_by_table ORDER BY sum_timer_wait DESC; +------------------------------------------------------+------------+-------------+-------------+----------------+ | object_name | COUNT_READ | COUNT_WRITE | COUNT_FETCH | SUM_TIMER_WAIT | +------------------------------------------------------+------------+-------------+-------------+----------------+ | books | 1 | 1 | 1 | 14683357736 | | dd_properties | 0 | 0 | 0 | 0 |
9、哪个索引访问最多？mysql> SELECT OBJECT_NAME,INDEX_NAME,COUNT_FETCH,COUNT_INSERT,COUNT_UPDATE,COUNT_DELETE FROM table_io_waits_summary_by_index_usage ORDER BY SUM_TIMER_WAIT DESC;
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| OBJECT_NAME | INDEX_NAME | COUNT_FETCH | COUNT_INSERT | COUNT_UPDATE | COUNT_DELETE |
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| books | NULL | 1 | 1 | 0 | 0 |10、哪个索引从来没有用过？
mysql> SELECT OBJECT_SCHEMA,OBJECT_NAME,INDEX_NAME FROM table_io_waits_summary_by_index_usage WHERE INDEX_NAME IS NOT NULL AND COUNT_STAR = 0 AND OBJECT_SCHEMA <> 'mysql' ORDER BY OBJECT_SCHEMA,OBJECT_NAME;
+--------------------+------------------------------------------------------+----------------------------------+
| OBJECT_SCHEMA | OBJECT_NAME | INDEX_NAME |
+--------------------+------------------------------------------------------+----------------------------------+
| cara_testing_db | books | PRIMARY |
| performance_schema | accounts | ACCOUNT |11、哪个等待事件消耗时间最多？
mysql> SELECT EVENT_NAME,COUNT_STAR,SUM_TIMER_WAIT,AVG_TIMER_WAIT FROM events_waits_summary_global_by_event_name WHERE event_name != 'idle' ORDER BY SUM_TIMER_WAIT DESC ;
+---------------------------------------------------------------------+------------+----------------+----------------+
| EVENT_NAME | COUNT_STAR | SUM_TIMER_WAIT | AVG_TIMER_WAIT |
+---------------------------------------------------------------------+------------+----------------+----------------+
| wait/io/file/innodb/innodb_data_file | 1103 | 686179063712 | 622102240 |
| wait/io/file/innodb/innodb_dblwr_file | 30 | 118918612832 | 3963953732 |
| wait/io/file/innodb/innodb_log_file | 109 | 66884431760 | 613618552 |12、剖析某条SQL的执行情况，包括statement信息，stege信息，wait信息
mysql> SELECT EVENT_ID,sql_text FROM events_statements_history WHERE sql_text LIKE '%count(*)%';
+----------+----------------------------+
| EVENT_ID | sql_text |
+----------+----------------------------+
| 155 | select count(*) from books |
+----------+----------------------------+
1 row in set (0.00 sec)13、查看每个阶段的时间消耗
mysql> SELECT event_id,EVENT_NAME,SOURCE,TIMER_END - TIMER_START FROM events_stages_history_long WHERE NESTING_EVENT_ID = 1553
-> ;
Empty set (0.01 sec)14、查看每个阶段的锁等待情况
mysql> SELECT event_id,event_name,source,timer_wait,object_name,index_name,operation,nesting_event_id FROM events_waits_history_long;
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Do everything well - 查看是否当前数据库是否支持
