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- Owner of the constraint definition. 約束定義的所有者。
- The following excerpt of a CREATE TABLE statement shows the definition of the Name column, specifying a UNIQUE constraint on this column to make sure the values are unique. 一個CREATE TABLE語句的以下節選顯示Name列的定義,對該列指定了UNIQUE約束,以確保值是唯一的。
- This class can be used to identify a unique constraint among a set of elements. 此類可用於標識一組元素中的唯一約束。
- The Unique Constraint or Foreign Key Constraint dialog box is displayed. 即顯示「唯一約束」或「外鍵約束」對話框。
- A computed column cannot be used as a DEFAULT or FOREIGN KEY constraint definition or with a NOT NULL constraint definition. 計算列不能用作DEFAULT或FOREIGN KEY約束定義,也不能與NOT NULL約束定義一起使用。
- The ALTER INDEX statement can be used to rebuild an index part of a constraint definition; the constraint does not have to be dropped and added again with ALTER TABLE. ALTER INDEX語句可用於重新生成約束定義的索引部分;而不必再使用ALTER TABLE來刪除和添加約束。
- Index imposing the UNIQUE constraint on the column designated as the unique key column. 對於指定為唯一鍵列的列施加UNIQUE約束的索引。
- Add or drop PRIMARY KEY or UNIQUE constraints. 添加或刪除PRIMARY KEY或UNIQUE約束。
- Unique constraints are also called keys. 唯一約束也稱為鍵。
- However, changing the length of a variable-length column used in a CHECK or UNIQUE constraint is allowed. 但是,允許更改用於CHECK或UNIQUE約束中的長度可變的列的長度。
- This set of columns may be generated from a base table primary key, a unique constraint or a unique index. 這組列可以從基表主鍵、唯一約束或唯一索引生成。
- All of the tables in the main data connection must contain a primary key, unique constraint, or unique index. 主數據連接中的所有表都必須包含一個主鍵、唯一約束或唯一索引。
- Columns of a unique index are allowed to be NULL, while columns in a unique constraint are not. 唯一索引的列可以為NULL,而唯一約束的列不能為NULL。
- In order to create a foreign key relationship, at least one of the two tables must have a primary key or unique constraint defined. 要創建外鍵關係,兩個表中必須至少有一個定義了主鍵或唯一約束。
- A unique index, UNIQUE constraint, or PRIMARY KEY constraint cannot be created if duplicate key values exist in the data. 如果數據中存在重複的鍵值,則不能創建唯一索引、UNIQUE約束或PRIMARY KEY約束。
- An index created as part of a PRIMARY KEY or UNIQUE constraint is automatically given the same name as the constraint name. 創建為PRIMARY KEY或UNIQUE約束的一部分的索引將自動給定與約束名稱相同的名稱。
- Create a unique constraint to ensure no duplicate values are entered in specific columns that do not participate in a primary key. 創建唯一約束可確保在不參與主鍵的特定列中不輸入重複值。
- When you attach a unique constraint to a column allowing null values, you ensure that at most one row will have a null value in the constrained column. 當將唯一約束附加到允許空值的列時,請確保在約束的列中最多有一行包含空值。
- Because the Regular Expression generator is not guaranteed to produce unique values, you cannot use it to fill a user-defined type column that has a unique constraint. 由於正則表達式生成器無法保證生成唯一值,因此您不能使用它來填充具有唯一約束的用戶定義的類型列。
- If a table already exists, you can add a UNIQUE constraint, provided that the column or combination of columns that make up the UNIQUE constraint contains only unique values. 如果表已經存在,可以添加UNIQUE約束(假設組成UNIQUE約束的列或列組合僅包含唯一的值)。
