For information on unique constraints in Azure Synapse Analytics, seePrimary key, foreign key, and unique key in Azure Synapse Analytics. Permissions Requires ALTER permission on the table. Use SQL Server Management Studio (SSMS) Create a unique constraint using SSMS ...
This topic describes how to create a unique index on a table in SQL Server by using SQL Server Management Studio or Transact-SQL. A unique index guarantees that the index key contains no duplicate values and therefore every row in the table is in some way unique. There are no significant ...
key_name Specifies the unique name by which the symmetric key is known in the database. This is a required parameter. Temporary keys are designated when thekey_namebegins with one number (#) sign. For example,#temporaryKey900007. You can't create a symmetric key that has a name that sta...
SQL 复制 CREATE INDEX index1 ON schema1.table1 (column1); 在表上创建聚集索引,并为表使用由 3 个部分组成的名称 SQL 复制 CREATE CLUSTERED INDEX index1 ON database1.schema1.table1 (column1); 使用唯一约束创建非聚集索引并指定排序顺序 SQL 复制 CREATE UNIQUE INDEX index1 ON schema1.tab...
159 160 一个PRIMARY KEY 可以是一个多列索引。然而,你不能在一个列规格说明中使用 PRIMARY KEY 键属性来创建一个多列索引。这样做将仅仅标记单个列做为主键。你必须使用 PRIMARY KEY(index_col_name, ...) 句法。 161 162 如果PRIMARY 或UNIQUE 键只由一个列组成,并且列类型是整型,你可以用 _rowid 引用...
Example 3:The following example shows how to use the same sequence number as a unique key value in two separate tables by referencing the sequence number with a NEXT VALUE expression for the first row to generate the sequence value and with a PREVIOUS VALUE expression for the other rows to ...
UNIQUE KEY只能在sql_compatibility='MYSQL'时使用,与UNIQUE语义相同。 PRIMARY KEY index_parameters PRIMARY KEY ( column_name [, ... ] ) index_parameters 主键约束声明表中的一个或者多个字段只能包含唯一的非NULL值。 一个表只能声明一个主键。 REFERENCES 当前版本分布式数据库暂不支持REFERENCES子句。 DEFER...
Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance This topic describes how to create a unique index on a table in SQL Server by using SQL Server Management Studio or Transact-SQL. A unique index guarantees that the index key contains no duplicate values and therefore every...
To create a unique index on a table, using: SQL Server Management Studio Transact-SQL Before You Begin Benefits of a Unique Index Multicolumn unique indexes guarantee that each combination of values in the index key is unique. For example, if a unique index is created on a combination ofLas...
UNIQUE 如果指定了 ONtable-name,那么 UNIQUE 将阻止表的两行或更多行具有相同的索引键值。 在更新行或插入新行的 SQL 语句末尾将强制实施唯一性。 在执行 CREATE INDEX 语句期间也将检查唯一性。 如果表中已经包含具有重复键值的行,那么不会创建索引。