How to get the Database Size

As a DBA it’s very important to know the exact size of the database that we are handling. First, to know the size of the information, second, to know the size of the space required to backup and third, to sizing the underlayer infrastructure.

Today we will learn how to get the database size in some RDBMS.

Oracle

col “Database Size” format a20
col “Free space” format a20
col “Used space” format a20
select round(sum(used.bytes) / 1024 / 1024 / 1024 ) || ‘ GB’ “Database Size”
, round(sum(used.bytes) / 1024 / 1024 / 1024 ) –
round(free.p / 1024 / 1024 / 1024) || ‘ GB’ “Used space”
, round(free.p / 1024 / 1024 / 1024) || ‘ GB’ “Free space”
from (select bytes
from v$datafile
union all
select bytes
from v$tempfile
union all
select bytes
from v$log) used
, (select sum(bytes) as p
from dba_free_space) free
group by free.p
/

MySQL

SELECT table_schema “Data Base Name”,
sum( data_length + index_length ) / 1024 / 1024 “Data Base Size in MB”,
sum( data_free )/ 1024 / 1024 “Free Space in MB”
FROM information_schema.TABLES
GROUP BY table_schema;

Postgres

SELECT pg_database.datname,
pg_size_pretty(pg_database_size(pg_database.datname)) AS size
FROM pg_database;

SQL Server

SELECT database_name = DB_NAME(database_id)
, log_size_mb = CAST(SUM(CASE WHEN type_desc = ‘LOG’ THEN size END) * 8. / 1024 AS DECIMAL(8,2))
, row_size_mb = CAST(SUM(CASE WHEN type_desc = ‘ROWS’ THEN size END) * 8. / 1024 AS DECIMAL(8,2))
, total_size_mb = CAST(SUM(size) * 8. / 1024 AS DECIMAL(8,2))
FROM sys.master_files WITH(NOWAIT)
WHERE database_id = DB_ID() — for current db
GROUP BY database_id
/

Note: all the above commands needs specials privileges or roles in every flavor.