If you want to see the impact of indexes on SELECT statements, you can run the same SELECT statement on "ggl_links" and "ggl_links_indexed" tables. See the tutorial exercise below:

USE GlobalGuideLineDatabase;

GO

-- Run SELECT on the table without indexes

DECLARE @start_time DATETIME, @end_time DATETIME;

SET @start_time = GETDATE();

SELECT TOP 3 counts, url FROM ggl_links

WHERE url LIKE 'a%'

ORDER BY counts DESC;

SET @end_time = GETDATE();

PRINT 'Milliseconds used: '+CONVERT(VARCHAR(20),

DATEDIFF(MILLISECOND,@start_time,@end_time));

GO

counts url

----------- ------------------------------------------------

999417 a ihgu migox mlqvi gvs n nmabwdk iehu ezjjv n l

999008 agqbr gkjwfpjvp z c cq k inen j ppjsu x iuk uhp

998471 a yiu squqco eih

Milliseconds used: 46