许多数据库的元数据都是存储在mysql中的，例如hive、startrockes，因此可以通过mysql中的“information_schema.TABLES”表来查询对应数据库或对应数据表的具体信息。
1、查询各个数据库中的数据条数和数据大小
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;2、查询各个数据表中的数据条数和数据大小
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;3、查看指定数据库容量大小
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
WHERE
table_schema = 'test';4、查看指定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
WHERE
table_schema = 'test'
ORDER BY
data_length DESC,
index_length DESC;5、查看指定数据库各表的列数
SELECT TABLE_NAME, COUNT(*) AS COLUMN_COUNT FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'test' GROUP BY TABLE_NAME;
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