Various ways to get sizing, counts, etc.

-- Total rows and size for an entire server, excluding system schemata, ordered by size DESC 
SELECT table_schema,table_name,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), 'G') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),'G') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * 1024), 2),'G') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES
 WHERE table_schema NOT IN ('mysql','performance_schema','information_schema') 
 GROUP BY table_schema,table_name
 ORDER BY SUM(data_length + index_length) DESC;

-- Total rows and size for an entire server, excluding system schemata, ordered by schema and table name 
 SELECT table_schema,table_name,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), 'G') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),'G') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * 1024), 2),'G') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES
 WHERE table_schema NOT IN ('mysql','performance_schema','information_schema') 
 GROUP BY table_schema,table_name
 ORDER BY table_schema,table_name;

-- Total rows and size
 SELECT COUNT(*) TABLES,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), 'G') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),'G') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * 1024), 2),'G') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES

-- Database wise report
 SELECT COUNT(*) TABLES, table_schema,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), 'G') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),'G') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * 1024), 2),'G') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES
 GROUP BY table_schema
 ORDER BY SUM(data_length + index_length) DESC

-- Database wise report in MB
 SELECT COUNT(*) TABLES, table_schema,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 ),2), 'M') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 ), 2),'M') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 ), 2),'M') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES
 GROUP BY table_schema
 ORDER BY SUM(data_length + index_length) DESC

-- Engine wise breakup
 SELECT ENGINE, COUNT(*) TABLES,
 CONCAT(ROUND(SUM(table_rows) / 1000000,2),'M') rows,
 CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), 'G') DATA,
 CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),'G') idx,
 CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * 1024), 2),'G') total_size,
 ROUND(SUM(index_length) / SUM(data_length),2) idxfrac
 FROM information_schema.TABLES
 GROUP BY engine ORDER BY sum(data_length+index_length) DESC

-- Top 30 tables
 SELECT table_schema, table_name, engine, table_rows,
 CONCAT(ROUND(data_length / (1024 * 1024),2),'MB') AS DATA,
 CONCAT(ROUND((data_length + index_length) / (1024 * 1024), 2),'MB') AS total_size
 FROM INFORMATION_SCHEMA.TABLES
 ORDER BY data_length DESC LIMIT 30

-- List of Full Text Indexes
 SELECT TABLE_SCHEMA, TABLE_NAME, INDEX_NAME, SEQ_IN_INDEX, COLUMN_NAME, CARDINALITY, NULLABLE
 FROM statistics
 WHERE index_type LIKE 'FULLTEXT%' ORDER BY TABLE_SCHEMA, TABLE_NAME

-- The number of columns for each datatype
 SELECT DATA_TYPE, COUNT(*) AS mycount
 FROM `COLUMNS`
 WHERE TABLE_SCHEMA NOT IN ('information_schema','mysql')
 GROUP BY DATA_TYPE ORDER BY mycount DESC

-- The number of columns for each datatype with size (replace my_database)
 SELECT TABLE_SCHEMA, COLUMN_TYPE, count(*) FROM `COLUMNS`
 GROUP BY COLUMN_TYPE HAVING TABLE_SCHEMA = 'my_database'

-- Blob, Float and Double Data types details
 SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, ORDINAL_POSITION, COLUMN_DEFAULT,
 IS_NULLABLE, NUMERIC_PRECISION, COLUMN_TYPE, COLUMN_KEY
 FROM COLUMNS
 WHERE DATA_TYPE IN ('FLOAT','BLOB','DOUBLE')
 AND TABLE_SCHEMA != 'mysql'
 ORDER BY DATA_TYPE, COLUMN_TYPE

--All tables with no primary key
use INFORMATION_SCHEMA;
 select CONCAT(t.table_schema,".",t.table_name) as tbl
 from INFORMATION_SCHEMA.TABLES AS t
 LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c
 ON (t.TABLE_NAME=c.TABLE_NAME
 AND c.CONSTRAINT_SCHEMA=t.TABLE_SCHEMA
 AND constraint_name='PRIMARY')
 WHERE t.table_schema!="information_schema"
 AND constraint_name IS NULL;

-- All tables and their primary keys, if exist:
use INFORMATION_SCHEMA;
 select CONCAT(t.table_schema,".",t.table_name) as tbl,
 c.column_name,c.constraint_name
 from INFORMATION_SCHEMA.TABLES AS t
 LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c
 ON (t.TABLE_NAME=c.TABLE_NAME
 AND c.CONSTRAINT_SCHEMA=t.TABLE_SCHEMA
 AND constraint_name='PRIMARY')
 WHERE t.table_schema!="information_schema"
 order by constraint_name;

-- Foreign Key constraints for Database dbName
SELECT A.TABLE_SCHEMA AS FKTABLE_SCHEM, A.TABLE_NAME AS FKTABLE_NAME, A.COLUMN_NAME AS FKCOLUMN_NAME,
 A.REFERENCED_TABLE_SCHEMA AS PKTABLE_SCHEM, A.REFERENCED_TABLE_NAME AS PKTABLE_NAME,
 A.REFERENCED_COLUMN_NAME AS PKCOLUMN_NAME, A.CONSTRAINT_NAME AS FK_NAME
 FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE A, INFORMATION_SCHEMA.TABLE_CONSTRAINTS B
 WHERE A.TABLE_SCHEMA = B.TABLE_SCHEMA AND A.TABLE_NAME = B.TABLE_NAME
 AND A.CONSTRAINT_NAME = B.CONSTRAINT_NAME AND B.CONSTRAINT_TYPE IS NOT NULL
 HAVING PKTABLE_SCHEM IS NOT NULL
 and A.TABLE_SCHEMA = 'dbName'
 ORDER BY A.TABLE_SCHEMA, A.TABLE_NAME, A.ORDINAL_POSITION limit 1000