The Distinct keyword can remove the repeated row from the results of the SELECT statement. If Distinct is not specified, all rows will be returned, including repeated rows. For example, if Distinct is not used when selecting all author IDs in Titleauthor, then the following line will be returned (including some repetitive rows):
USE PUBS
SELECT AU_ID
From titleauthor
The following is the result set:
AU_ID
-----------
172-32-1176
213-46-8915
213-46-8915
238-95-7766
267-41-2394
267-41-2394
274-80-9391
409-56-7008
427-17-2319
472-27-2349
486-29-1786
486-29-1786
648-92-1872
672-71-3249
712-45-1867
722-51-5454
724-80-9391
724-80-9391
756-30-7391
807-91-6654
846-92-7186
899-46-2035
899-46-2035
998-72-3567
998-72-3567
(25 row (s) affected)
After using Distinct, you can remove duplicate, and only the only author ID:
USE PUBS
SELECT DISTINCT AU_ID
From titleauthor
The following is the result set:
AU_ID
-----------
172-32-1176
213-46-8915
238-95-7766
267-41-2394
274-80-9391
409-56-7008
427-17-2319
472-27-2349
486-29-1786
648-92-1872
672-71-3249
712-45-1867
722-51-5454
724-80-9391
756-30-7391
807-91-6654
846-92-7186
899-46-2035
998-72-3567
(19 row (s) affected)
