In SQL Server, you can use the CREATE TABLE statement to establish a unique constraint. This constraint ensures that all values in a column (or a combination of columns) are unique. Here is an example:<\/p>\n
CREATE TABLE \u8868\u540d (\r\n\u5217\u540d1 \u6570\u636e\u7c7b\u578b CONSTRAINT \u7ea6\u675f\u540d UNIQUE,<\/p>\r\n
\u5217\u540d2 \u6570\u636e\u7c7b\u578b,<\/p>\r\n
\u2026\r\n);<\/p><\/pre>\n
In this case, “table name” is the name of the table to be created, “column name 1” is the name of the column to set a unique constraint, “data type” is the data type of the column, “constraint name” is the name of the constraint, and “UNIQUE” specifies it as a unique constraint. If you want to add a unique constraint to an already existing table, you can use the ALTER TABLE statement.<\/p>\n
ALTER TABLE \u8868\u540d ADD CONSTRAINT \u7ea6\u675f\u540d UNIQUE (\u5217\u540d1, \u5217\u540d2, \u2026);<\/pre>\nPlease note that the constraint name can be changed as needed to ensure uniqueness. Additionally, you can use the PRIMARY KEY keyword in the CREATE TABLE or ALTER TABLE statement to set a primary key constraint, which will also automatically create a unique constraint.<\/p>\n
CREATE TABLE \u8868\u540d (<\/p>\r\n
\u5217\u540d \u6570\u636e\u7c7b\u578b PRIMARY KEY,<\/p>\r\n
\u2026\r\n);\r\n\u6216\r\nALTER TABLE \u8868\u540d ADD CONSTRAINT \u7ea6\u675f\u540d PRIMARY KEY (\u5217\u540d);<\/p><\/pre>\n
The above is the way to set a unique constraint at the table level. If you want to set a unique constraint at the column level, you can use the UNIQUE keyword in the column definition.<\/p>\n
CREATE TABLE \u8868\u540d (<\/p>\r\n
\u5217\u540d1 \u6570\u636e\u7c7b\u578b UNIQUE,<\/p>\r\n
\u5217\u540d2 \u6570\u636e\u7c7b\u578b,<\/p>\r\n
\u2026\r\n);<\/p><\/pre>\n","protected":false},"excerpt":{"rendered":"
In SQL Server, you can use the CREATE TABLE statement to establish a unique constraint. This constraint ensures that all values in a column (or a combination of columns) are unique. Here is an example: CREATE TABLE \u8868\u540d ( \u5217\u540d1 \u6570\u636e\u7c7b\u578b CONSTRAINT \u7ea6\u675f\u540d UNIQUE, \u5217\u540d2 \u6570\u636e\u7c7b\u578b, \u2026 ); In this case, “table name” is the name of the table to be created, “column […]<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-27624","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"\n
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Here is an example: CREATE TABLE \u8868\u540d ( \u5217\u540d1 \u6570\u636e\u7c7b\u578b CONSTRAINT \u7ea6\u675f\u540d UNIQUE, \u5217\u540d2 \u6570\u636e\u7c7b\u578b, \u2026 ); In this case, “table name” is the name of the table to be created, “column […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - Silicon Cloud\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/SiliCloudGlobal\/\" \/>\n<meta property=\"article:published_time\" content=\"2024-03-16T08:50:49+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-03-22T11:29:14+00:00\" \/>\n<meta name=\"author\" content=\"Emily Johnson\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:site\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Emily Johnson\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/\"},\"author\":{\"name\":\"Emily Johnson\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/#\/schema\/person\/3b041b19cffc258705478ecfab895378\"},\"headline\":\"How to set a unique constraint in SQL Server?\",\"datePublished\":\"2024-03-16T08:50:49+00:00\",\"dateModified\":\"2024-03-22T11:29:14+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/\"},\"wordCount\":196,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/#organization\"},\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/\",\"url\":\"https:\/\/www.silicloud.com\/blog\/how-to-set-a-unique-constraint-in-sql-server\/\",\"name\":\"How to set a unique constraint in SQL Server? 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