CONSTRAINT名字 (可选)指定约束的名称。 该名称在架构中必须唯一。 如果未提供任何名称,Azure Databricks 会生成一个。 PRIMARY KEY ( key_column [ TIMESERIES ] [, ...] ) [ constraint_option [...] ] 适用于:仅 Unity Catalog 向Delta Lake 表添加主键约束。 一个表最多只能有一个主键。
CHECK constraint is used to limit the range of the values, that can be entered for a column. Let's say, we have an integer AGE column, in a table. The AGE in general cannot be less than ZERO and at the same time cannot be greater than 150. But, since AGE is an integer column ...
We can also add theUNIQUEconstraint to an existing column using theALTER TABLEcommand. For example, For a Single Column -- add unique constraint to an existing columnALTERTABLECollegesADDUNIQUE(college_id); Here, the SQL command adds theUNIQUEconstraint to thecolleges_idcolumn in the existingColl...
Using ALTER TABLEand ADD CONSTRAINT, you can add aforeign key to an existing table. The syntax for doing so is as follows: ALTERTABLEtable_nameADDCONSTRAINTconstraint_nameFOREIGNKEY(column_name)REFERENCES[ schema_name.] referenced_table_name [ ( ref_column ) ] This example adds aforeign key ...
Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Specifies the properties of a PRIMARY KEY, FOREIGN KEY, UNIQUE, or CHECK constraint that is part of a new column definition added to a table by using ALTER TABLE. Note For Microsoft Fabric, visit ALTER TABLE column_...
ADD column_name tada_type NOT NULL CONSTRAINT constraint_name DEFAULT default_value; If you set the new column nullable, that column value for all existing rows will be NULL instead of the default value. In that case, you can addWITH VALUESto the statement: ...
Add a LONG, LOB, or object type column or change the datatype of an external table column to any of these datatypes. Add a constraint to an external table. Modify the storage parameters of an external table. Specify LOGGING or NOLOGGING. Specify MOVE Note: If you alter a table...
this code will likely either directly solve or pave the path to solving#47719as it will drop the constraint in one phase before dropping the column - thus the constraint will certainly have been dropped on all nodes by the time the backfill to drop the column tries to run. It's possible...
How to: To SQL add a column with a default value is a simple operation in SQL. Let us set up a ‘student’ table as below:
AlwaysOn 可用性群組支持查詢可讀取次要複本上的數據行存放區索引。 Multiple Active Result Sets (MARS) 支援列存儲索引。 全新動態管理檢視sys.dm_db_column_store_row_group_physical_stats (Transact-SQL)提供資料列群組層級的效能疑難排解資訊。 數據行存放區索引上的所有查詢都可以在批次模式中執行。 先前,只有...