CONSTRAINTname 選擇性地指定條件約束的名稱。 名稱在架構內必須是唯一的。 如果未提供任何名稱,Azure Databricks 將會產生一個名稱。 PRIMARY KEY ( key_column [ TIMESERIES ] [, ...] ) [ constraint_option [...] ] 適用於:僅限 Unity Catalog ...
ConstraintCollection.cs 使用指定的名稱、UniqueConstraint和表示資料行是否為主索引鍵的值,來建構新的DataColumn,並將它加入至集合中。 C# publicSystem.Data.ConstraintAdd(string? name, System.Data.DataColumn column,boolprimaryKey); 參數 name String
however, use the MODIFY clause of the ALTER TABLE statement to define a NOT NULL constraintor a NULL constraint (but not both)on a column in a RAW table. For the syntax to add a NULL or NOT NULL constraint on a column in an existing table, seeMODIFY Clause...
AddDefaultConstraint 方法 將預設條件約束加入至資料行。 命名空間:Microsoft.SqlServer.Management.Smo 組件:Microsoft.SqlServer.Smo (在 Microsoft.SqlServer.Smo.dll 中) 語法
To add a constraint to an existing table use the alter table statement with the add constraint command. There are four different types of constraints:Primary Key Constraints – Enforces unique values for specified column, can be referenced. Foreign Key Constraints – Enforces a reference to a ...
Constraint Add (string? name, System.Data.DataColumn column, bool primaryKey); Parameters name String The name of the UniqueConstraint. column DataColumn The DataColumn to which the constraint applies. primaryKey Boolean Specifies whether the column should be the primary key. If true, the ...
Using ALTER TABLE ADD CONSTRAINT, any of bellow constraints can be added to existing table NOT NULL CHECK UNIQUE PRIMARY KEY FOREIGN KEY Consider that you already have the following employee table.Add UNIQUE Constraint The UNIQUE constraint ensures that the values of a column must be unique and ...
Introduction to the PostgreSQL ADD COLUMN statement To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_name ADD COLUMN new_column_name data_type constraint; In this syntax: First, specify the name of the table to which you...
ADD column_name datatype [DEFAULT default_value] [NULL|NOT NULL] [CONSTRAINT constraint_name] [column_constraint_clause]; Swap table_name with the table’s name to which you wish to add the column(s). The column_name specifies the name of the column you wish to add to the table. This...
If it is there, I want to drop it first then add it. But how can I know its existance? Is there any If and Else clause to judge it? Code Snippet if ...exists drop ... Else alter table xxxx add constraint aaa unique(SomeColumn) Thanks...