How does select operation perform in RDBMS?

Answer 1

Data is contained in tables. Tables have fields (columns) that hold rows of data. Here is an example of the field in a table: >>invoke $d001.vssdata.lastactv;
-- Definition of table \BEAST.$D001.VSSDATA.LASTACTV
-- Definition current at 15:46:25 - 06/25/07

(
STYLE_NBR INT NO DEFAULT NOT NULL
, ITEM_NBR INT NO DEFAULT NOT NULL
, SHOP_NBR SMALLINT NO DEFAULT NOT NULL
, COLOR_NBR SMALLINT NO DEFAULT NOT NULL
, SIZE_NBR SMALLINT NO DEFAULT NOT NULL
, LAST_ACTIVITY_DATE DATETIME YEAR TO DAY NO DEFAULT NOT NULL
, REGULAR_EOP_STOCK_UNITS INT NO DEFAULT NOT NULL
, REGULAR_EOP_STOCK_RETAIL NUMERIC( 18, 2) NO DEFAULT NOT NULL
, REGULAR_EOP_STOCK_COST NUMERIC( 18, 2) NO DEFAULT NOT NULL
, REDLINE_EOP_STOCK_UNITS INT NO DEFAULT NOT NULL
, REDLINE_EOP_STOCK_RETAIL NUMERIC( 18, 2) NO DEFAULT NOT NULL
, REDLINE_EOP_STOCK_COST NUMERIC( 18, 2) NO DEFAULT NOT NULL
, MODEL_INVENTORY INT NO DEFAULT NOT NULL
, PCT_STK_NUMERATOR SMALLINT NO DEFAULT NOT NULL
, PCT_STK_DENOMINATOR SMALLINT NO DEFAULT NOT NULL
, LOAD_STYLE INT NO DEFAULT NOT NULL
, INTRANSIT_UNITS INT NO DEFAULT NOT NULL
, OWNER_NBR SMALLINT NO DEFAULT NOT NULL
)
>>
CODE EOF LAST MODIFIED OWNER RWEP PExt SE Say you wanted to know the stock cost between May 1 and May 31. You would query that table for that data. select style_number, regular_eop_stock_cost, owner_nbr from $data.vssdata.lastactv where last_activity_date between "05-01-07" and "05-31-07"; Depending on how large the table is, how fragmented, and last update stats, it could return the data quickly or it could take an hour or more. The date format in the query depends on the database.