ANALYZE TABLE SALES_HISTORY COMPUTE STATISTICS;
ANALYZE TABLE SALES_HISTORY_COMP COMPUTE STATISTICS;

SELECT TABLE_NAME, BLOCKS, NUM_ROWS, COMPRESSION
FROM USER_TABLES
WHERE TABLE_NAME LIKE 'SALES_HIST%';

TABLE_NAME                BLOCKS   NUM_ROWS   COMPRESSION
------------------        ------  --------   -----------
SALES_HISTORY              12137    1000000   DISABLED
SALES_HISTORY_COMP          6188    1000000   ENABLED

codeLISTING 4:  Comparing queries on uncompressed and compressed tables

TKPROF results of the query on the uncompressed table:

SELECT SALE_DATE, COUNT(*) FROM SALES_HISTORY GROUP BY SALE_DATE;

call     count   cpu elapsed  disk      query    current   rows
------- ------  ---- -------  ----- ---------- ----------  -----
Parse        1  0.00    0.01     0          0          0      0
Execute      1  0.00    0.00     0          0          0      0
Fetch        2  5.22   13.76  10560      12148          0      1
------- ------  ---- -------  ----- ---------- ----------  -----
total        4  5.22   13.78  10560      12148          0      1


TKPROF results of the query on the compressed table:

SELECT SALE_DATE, COUNT(*) FROM SALES_HISTORY_COMP GROUP BY SALE_DATE;

call     count   cpu elapsed  disk      query    current   rows
------- ------  ---- ------- ----- ---------- ----------  -----
Parse        1  0.00    0.00     0          0          0      0
Execute      1  0.00    0.00     0          0          0      0
Fetch        2  5.27    7.20  6082       6091          0      1
------- ------  ---- ------- ----- ---------- ----------  -----
total        4  5.27    7.20  6082       6091          0      1