{"id":132,"date":"2014-04-22T12:45:00","date_gmt":"2014-04-22T11:45:00","guid":{"rendered":"https:\/\/debuggersspace.com\/index.php\/2014\/04\/22\/difference-between-primary-key-and-unique-key-in-sql\/"},"modified":"2014-04-22T12:45:00","modified_gmt":"2014-04-22T11:45:00","slug":"difference-between-primary-key-and-unique-key-in-sql","status":"publish","type":"post","link":"https:\/\/debuggersspace.com\/index.php\/2014\/04\/22\/difference-between-primary-key-and-unique-key-in-sql\/","title":{"rendered":"Difference between Primary key and Unique Key in Sql??"},"content":{"rendered":"
\n
\n \t<\/i> Read Time:<\/span>41 Second <\/div>\n\n <\/div>
\n
\n
\nPrimary Key<\/span><\/div>\n
\nUnique Key<\/span><\/div>\n<\/div>\n
\n
\nPrimary Key can’t accept null values.<\/span><\/div>\n
\nUnique key can accept only one null value.<\/span><\/div>\n<\/div>\n
\n
\nBy default, Primary key is clustered index <\/span>
\nand data in the database table is physically <\/span>
\norganized in the sequence of clustered index.<\/span><\/div>\n
\nBy default, Unique key is a unique non-clustered index.  <\/span><\/div>\n<\/div>\n
\n
\nWe can have only one Primary key in a table.<\/span><\/div>\n
\nWe can have more than one unique key in a table.        <\/span><\/div>\n<\/div>\n
\n
\nPrimary key can be made foreign key into      another table.<\/span><\/div>\n
\nIn SQL Server, Unique key can be made foreign key into another table.<\/span><\/div>\n<\/div>\n

Example:<\/b><\/span><\/span><\/p>\n

\nCreate<\/span> table<\/span> Student<\/span><\/div>\n
\n(<\/span><\/div>\n
\nStuId int<\/span> primary<\/span> key<\/span>,<\/span> —- Define Primary Key<\/span><\/span><\/div>\n
\nStuName varchar<\/span>(<\/span>50)<\/span> Not<\/span> Null,<\/span><\/span><\/div>\n
\nContactNo int<\/span> Unique<\/span> — Define Unique Key<\/span><\/span><\/div>\n
\n)<\/span><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Primary Key Unique Key Primary Key can’t accept null values. Unique key can accept only one null value. By default, Primary key is clustered index and data in the database table is physically organized in the sequence of clustered index. By default, Unique key is a unique non-clustered index.   We can have only one […]<\/p>\n","protected":false},"author":43,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","footnotes":""},"categories":[27],"tags":[],"class_list":["post-132","post","type-post","status-publish","format-standard","hentry","category-sql"],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false},"uagb_author_info":{"display_name":"Himanshu Namdeo","author_link":"https:\/\/debuggersspace.com\/author\/admin\/"},"uagb_comment_info":0,"uagb_excerpt":"Primary Key Unique Key Primary Key can’t accept null values. Unique key can accept only one null value. By default, Primary key is clustered index and data in the database table is physically organized in the sequence of clustered index. By default, Unique key is a unique non-clustered index.   We can have only one…","_links":{"self":[{"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/posts\/132"}],"collection":[{"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/users\/43"}],"replies":[{"embeddable":true,"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/comments?post=132"}],"version-history":[{"count":0,"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/posts\/132\/revisions"}],"wp:attachment":[{"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/media?parent=132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/categories?post=132"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/debuggersspace.com\/index.php\/wp-json\/wp\/v2\/tags?post=132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}