以下是 MySQL 数据库空间大小查询与管理的常用方法，基于最新实践整理：

一、查询数据库空间大小

1. 查看所有数据库空间

SELECT
  table_schema AS '数据库',
  SUM(table_rows) AS '记录数',
  SUM(TRUNCATE(data_length/1024/1024,2)) AS '数据容量(MB)',
  SUM(TRUNCATE(index_length/1024/1024,2)) AS '索引容量(MB)',
  SUM(TRUNCATE((data_length+index_length)/1024/1024,2)) AS '总大小(MB)'
FROM information_schema.tables
GROUP BY table_schema
ORDER BY SUM(data_length) DESC;

此语句统计所有数据库的总数据量、索引量及碎片空间，结果按数据容量降序排列。

使用：
SELECT
  table_schema AS '数据库',
  SUM(table_rows) AS '记录数',
  SUM(TRUNCATE(data_length/1024/1024,2)) AS '数据容量(MB)',
  SUM(TRUNCATE(index_length/1024/1024,2)) AS '索引容量(MB)',
  SUM(TRUNCATE((data_length+index_length)/1024/1024,2)) AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema='sftzhzx_jy-241220'
GROUP BY table_schema
ORDER BY SUM(data_length) DESC;

SELECT
  table_schema AS '数据库',
  SUM(table_rows) AS '记录数',
  SUM(TRUNCATE(data_length/1024/1024,2)) AS '数据容量(MB)',
  SUM(TRUNCATE(index_length/1024/1024,2)) AS '索引容量(MB)',
  SUM(TRUNCATE((data_length+index_length)/1024/1024,2)) AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema='sftzhzx_jd'
GROUP BY table_schema
ORDER BY SUM(data_length) DESC;

2. 查看指定数据库空间

SELECT
  table_schema AS '数据库',
  SUM(data_length + index_length)/1024/1024 AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema = 'your_database_name'
GROUP BY table_schema;

替换 your_database_name 后，可获取特定数据库的总空间占用。

使用：
SELECT
  table_schema AS '数据库',
  SUM(data_length + index_length)/1024/1024 AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema = 'sftzhzx_jy-241220'
GROUP BY table_schema;

SELECT
  table_schema AS '数据库',
  SUM(data_length + index_length)/1024/1024 AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema = 'sftzhzx_jd'
GROUP BY table_schema;

二、查询表级空间占用

1. 查看数据库中所有表空间

SELECT
  table_name AS '表名',
  TRUNCATE(data_length/1024/1024,2) AS '数据容量(MB)',
  TRUNCATE(index_length/1024/1024,2) AS '索引容量(MB)',
  TRUNCATE((data_length+index_length)/1024/1024,2) AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema = 'your_database_name'
ORDER BY (data_length + index_length) DESC;

用于分析指定数据库内各表的空间分布，识别大表。

2. 精确查询单表空间

SELECT
  table_name AS '表名',
  TRUNCATE((data_length + index_length)/1024/1024,2) AS '总大小(MB)'
FROM information_schema.tables
WHERE table_schema = 'your_database_name'
  AND table_name = 'your_table_name';

适用于定位具体表的空间占用情况。

三、空间管理建议

1、自动扩展配置

在 my.cnf 配置文件中设置自动扩展参数，避免空间不足：

[mysqld]
innodb_data_file_path = ibdata1:10M:autoextend

2、独立表空间优化

启用独立表空间可提升管理灵活性：

SET GLOBAL innodb_file_per_table = 1;

3、定期清理碎片

对频繁更新的表执行优化命令：

OPTIMIZE TABLE your_table_name;

以上方法结合系统表查询与配置优化，可有效管理和监控数据库空间。

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