mysql的information_schema表

MySQL中 information_schema 为信息数据库，有其他数据库表的相关信息。

1 SELECT * FROM information_schema.INNODB_TRX;

查看当前运行的事务，可用于分析mysql执行卡顿时的原因。

2 查看所有数据库容量的大小

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)'
FROM
    information_schema. TABLES
GROUP BY
    table_schema
ORDER BY
    sum(data_length) DESC,
    sum(index_length) DESC;

3 查看所有数据库各表容量大小

SELECT
    table_schema AS '数据库',
    table_name AS '表名',
    table_rows AS '记录数',
    TRUNCATE (data_length / 1024 / 1024, 2) AS '数据容量(MB)',
    TRUNCATE (index_length / 1024 / 1024, 2) AS '索引容量(MB)'
FROM
    information_schema. TABLES
ORDER BY
    data_length DESC,
    index_length DESC;