Compress/Shrink SQL Server Database/Table/Index, tSql

When our database size was too large, we need to compress or shrink data to reduce the disk/file/database size. I will provide some guidance to reduce the database/index size to the minimal which ensure the high availability of disk space.

I will discuss below points to Compress as much as possible ...

1. Find the Tables need to Compress
2. Estimate the Compression rate/size.
3. Compress the Table Data in Page Level. (it can be in ROW level)
4. Compress the Index size in Page Level. (it can be in ROW level)
5. Compress/Shrink full database.

NOTE: If any table has Sparse Column, we can't compress that table/index directly.

1. First of all, we have to find the affected/large in size Tables. Use below SQL to Find the large Tables.

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-- Determine which tables to compress

SELECT  

    t.NAME AS TableName, 

    i.name as indexName, 

    sum(p.rows) as RowCounts, 

    sum(a.total_pages) as TotalPages, 

    sum(a.used_pages) as UsedPages, 

    sum(a.data_pages) as DataPages, 

    (sum(a.total_pages) * 8) / 1024 as TotalSpaceMB, 

    (sum(a.used_pages) * 8) / 1024 as UsedSpaceMB, 

    (sum(a.data_pages) * 8) / 1024 as DataSpaceMB  

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 

WHERE 

    t.NAME NOT LIKE 'dt%' AND 

    i.OBJECT_ID > 255 AND   

    -- i.index_id <= 1 

GROUP BY  

    t.NAME, i.object_id, i.index_id, i.name  

ORDER BY  

    object_name(i.object_id) 

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2. After getting the table and index list; Now we have to estimate the size compression, how much size we can reduce.

Use below SQL to check the reduced size.
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-- For Table Data Compression 
EXEC sp_estimate_data_compression_savings 
              @schema_name = 'dbo', 
              @object_name = 'DATABASE_NAME', 
              @index_id = NULL, -- For Table Data Compression
              @partition_number = NULL,
             @data_compression = 'Page' ;

-- For Index Data Compression 
EXEC sp_estimate_data_compression_savings 
              @schema_name = 'dbo', 
              @object_name = 'DATABASE_NAME', 
              @index_id = 1, -- Index ID -- For Index Data Compression
              @partition_number = NULL,

             @data_compression = 'Page' ;
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3. After making the final list of Table, we can now compress the table using below SQL
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ALTER TABLE dbo.TABLE_NAME REBUILD PARTITION = ALL WITH (DATA_COMPRESSION = PAGE);
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4. After Table Compression, we now can compress the Indexes (one by one) ..
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ALTER INDEX INDEX_NAME ON dbo.TABLE_NAME REBUILD PARTITION = ALL WITH (DATA_COMPRESSION = PAGE); 
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5. Finally we can Shrink/Compress the full database .. use below SQL ..
Bellow command have some other parameters, for details please check DBCC SHRINKDATABASE (Transact-SQL)
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DBCC SHRINKDATABASE(N'DATABASE_NAME');
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NOTE: You may use the procedure sp_spaceused to track the data size

all above is the example which I did for a database of 1 TB. You can choose your own compression strategy to compress the database or files.