Get size of tables from SQL Data base for D365FO

 In order to check the tables size, you need to open the SQL server Management Studio and execute the below query

1. In the Management Studio, click New Query or expand the Databases list and right click the needed database > New Query
2. In the query editor, execute the below query by putting the correct database name
   
   USE <DatabaseName>
   GO
   
   SELECT
   t.Name AS TableName,
   s.Name AS SchemaName,
   p.Rows AS RowCounts,
   SUM(a.total_pages) * 8 AS TotalSpaceKB,
   SUM(a.used_pages) * 8 AS UsedSpaceKB,
   (SUM(a.total_pages) - SUM(a.used_pages)) * 8 AS UnusedSpaceKB
   FROM
   sys.tables t
   INNER JOIN sys.indexes i ON t.object_id = i.object_id
   INNER JOIN sys.partitions p ON i.object_id = p.object_id AND i.index_id = p.index_id
   INNER JOIN sys.allocation_units a ON p.partition_id = a.container_id
   LEFT OUTER JOIN sys.schemas s ON t.schema_id = s.schema_id
   WHERE t.Name NOT LIKE 'dt%'
   AND t.is_ms_shipped = 0
   AND i.object_id > 255
   GROUP BY t.Name, s.Name, p.Rows
   ORDER BY SUM(a.used_pages) * 8 DESC;
   GO

3.Once the query is executed, you will get the list of tables sorted by its used space

Another one :

EXEC sp_spaceused 'generaljournalentry'

//for a specific table