Determining max database and table size supported and present size
Here are some nice queries I have used for years:

This reports the amount of data and indexes for each storage engine:

SELECT IFNULL(B.engine,'Total') "Storage Engine", CONCAT(LPAD(REPLACE(FORMAT(B.DSize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Data Size", CONCAT(LPAD(REPLACE(FORMAT(B.ISize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Index Size", CONCAT(LPAD(REPLACE(FORMAT(B.TSize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Table Size" FROM (SELECT engine,SUM(data_length) DSize,SUM(index_length) ISize,SUM(data_length+index_length) TSize FROM information_schema.tables WHERE table_schema NOT IN ('mysql','information_schema','performance_schema') AND engine IS NOT NULL GROUP BY engine WITH ROLLUP) B,
(SELECT 3 pw) A ORDER BY TSize;


This reports the amount of data and indexes for each database:

SELECT DBName,CONCAT(LPAD(FORMAT(SDSize/POWER(1024,pw),3),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Data Size",CONCAT(LPAD(FORMAT(SXSize/POWER(1024,pw),3),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Index Size",CONCAT(LPAD(FORMAT(STSize/POWER(1024,pw),3),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') "Total Size" FROM (SELECT IFNULL(DB,'All Databases') DBName,SUM(DSize) SDSize,SUM(XSize) SXSize,SUM(TSize) STSize FROM (SELECT table_schema DB,data_length DSize,index_length XSize,data_length+index_length TSize FROM information_schema.tables WHERE table_schema NOT IN ('mysql','information_schema','performance_schema')) AAA GROUP BY DB WITH ROLLUP) AA,
(SELECT 3 pw) BB ORDER BY (SDSize+SXSize);


This reports the amount of data and indexes for each database  by storage engine:

SELECT Statistic,DataSize "Data Size",IndexSize "Index Size",TableSize "Table Size" FROM (SELECT IF(ISNULL(table_schema)=1,10,0) schema_score,IF(ISNULL(engine)=1,10,0) engine_score,IF(ISNULL(table_schema)=1,'ZZZZZZZZZZZZZZZZ',table_schema) schemaname,IF(ISNULL(B.table_schema)+ISNULL(B.engine)=2,"Storage for All Databases",IF(ISNULL(B.table_schema)+ISNULL(B.engine)=1,CONCAT("Storage for ",B.table_schema),CONCAT(B.engine," Tables for ",B.table_schema))) Statistic,CONCAT(LPAD(REPLACE(FORMAT(B.DSize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') DataSize,CONCAT(LPAD(REPLACE(FORMAT(B.ISize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') IndexSize,CONCAT(LPAD(REPLACE(FORMAT(B.TSize/POWER(1024,pw),3),',',''),17,' '),' ',SUBSTR(' KMGTP',pw+1,1),'B') TableSize FROM (SELECT table_schema,engine,SUM(data_length) DSize,SUM(index_length) ISize,SUM(data_length+index_length) TSize FROM information_schema.tables WHERE table_schema NOT IN ('mysql','information_schema','performance_schema') AND engine IS NOT NULL GROUP BY table_schema,engine WITH ROLLUP) B,
(SELECT 3 pw) A) AA ORDER BY schemaname,schema_score,engine_score;


Please notice at the end of each query there is an inline query (SELECT 3 pw). The pw is simply an exponent used as a power of 1024. Here is how to use this:


(SELECT 0 pw) reports in bytes
(SELECT 1 pw) reports in kilobytes
(SELECT 2 pw) reports in megabytes
(SELECT 3 pw) reports in gigabytes
(SELECT 4 pw) reports in terabytes
(SELECT 5 pw) reports in petabytes (If you got this much data, write me or at least post the display in DBA.SE. I'm sure we'd all love to see that)


Give it a Try !!!

As for table limits, here are those limits for MyISAM and InnoDB.