15596 10 否 警告: 对具有行级别安全性的表使用 UNIQUE 索引、PRIMARY KEY 约束或 UNIQUE 约束可能导致信息泄漏。 15597 10 否 警告: 对具有行级别安全性的表使用 IDENTITY 列可能导致信息泄漏。 15598 10 否 警告: 对具有行级别安全性的表使用索引视图可能导致信息泄漏...
Therefore, even if the column has more than 200 unique values, the histogram might have fewer than 200 steps. For a column consisting of only unique values, then the consolidated histogram has a minimum of three steps.Note If the histogram has been built using a sample rather than fullscan...
Aliases must be unique within the view. If you omit the aliases, Oracle derives them from the columns or column aliases in the view's query. For this reason, you must use aliases if the view's query contains expressions rather than only column names. Restriction: You cannot specify an...
Only one PRIMARY KEY constraint can be created per table. UNIQUE A constraint that provides entity integrity for a specified column or columns through a unique index. A table can have multiple UNIQUE constraints. CLUSTERED | NONCLUSTERED Indicates that a clustered or a nonclustered index is ...
Can only be used with a FileTable. SET ( FILETABLE_DIRECTORY = directory_name ) Applies to: SQL Server (SQL Server 2012 (11.x) and later). Azure SQL Database doesn't support FILETABLE. Specifies the Windows-compatible FileTable directory name. This name should be unique among all the ...
Label names must be unique within a query batch or stored procedure. Error :The cursor is READ ONLY. Error :UNION ALL view 'address' is not updatable because a partitioning column was not found Error :Update or insert of view or function 'af' failed because it contains a derived or ...
1 Density defines the distribution of unique values that exist in the data, or the average number of duplicate values for a given column. As density decreases, selectivity of a value increases.The SQL Server Query Optimizer is important because it enables the database server to adjust ...
The Unicode Consortium allocates to each character a unique code point, which is a value in the range 000000 - 10FFFF. The most frequently used characters have code point values in the range 000000 - 00FFFF (65,536 characters) which fit into an 8-bit or 16-bit word in memory and on-...
3、unique key :唯一约束 列值不能重复 4、unsigned :无符号 针对数字列,非负数。 2)其他属性 1、key :索引 可以在某列上建立索引,来优化查询,一般是根据需要后添加 2、default :默认值 列中,没有录入值时,会自动使用default的值填充 3、auto_increment :自增长针对数字列,顺序的自动填充数据(默认是从1开...
Constraint: Options include Enable or Disable Single, Drop (delete a constraint), Add Check (add a check constraint), Add Foreign Key, and Add Unique. Privileges: If you are connected as a database user with sufficient privileges, you can Grant or Revoke privileges on the table to other us...