MySQL DB-size, tables size

Size of all tables in particular DB (change NEEDED_DB_NAME to needed):

SELECT table_name AS "Table", 

data_length+index_length AS "Size in bytes" 

FROM information_schema.TABLES 

WHERE table_schema = "NEEDED_DB_NAME" 

ORDER BY (data_length + index_length) DESC;

Size of all DB in MySQL:

SELECT table_schema AS "Database", 

ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS "Size (MB)" 

FROM information_schema.TABLES 

GROUP BY table_schema;

Count of rows of all tables in particular DB ((change NEEDED_DB_NAME to needed):

SELECT table_name AS "Table", 

table_rows AS "Rows" 

FROM information_schema.TABLES 

WHERE table_schema = "NEEDED_DB_NAME" 

ORDER BY table_rows DESC;

Table size description (depends on system block size):

1. index_length=data_length=16384 (total size is 32768) - empty table with index
2. index_length=0, data_length=16384 - empty table without index (only primary key can exist)

In MySQL (INNODB):

KEY=INDEX

PRIMARY KEY=special case of UNIQUE KEY (identifies that row and also data can't be NULL)

To check index, engine, index_length, data_length, create_time (change NEEDED_TABLE_NAME):

show table status like 'NEEDED_TABLE_NAME';