Databricks SQL Databricks Runtime 11.3 LTS 和更新版本 定義Delta Lake 數據表的資訊主鍵或參考外鍵條件約束。 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 ] [, ...] ...
Defines aninformationalprimary key orinformationalforeign key constraint for aDelta Laketable. Informational key constraints are not enforced but can improve performance by supportingquery optimizations. CONSTRAINTname Optionally specifies a name for the constraint. The name must be unique within the schema....
SQL EXEC ('CREATETABLESchemaName.TableName(col1intnotnullCONSTRAINTPK_col1 PRIMARYKEYCLUSTERED (col1) )') at LinkedServerName; EXEC ('INSERTINTOSchemaName.TableNameVALUES(1),(2),(3)') at LinkedServerName; 使用四部分名称查询数据: SQL ...
ADDCONSTRAINTpk_employeesPRIMARYKEY (employee_id); 在employees表中添加一个名为pk_employees的主键约束条 件,该约束条件应用于employee_id列。 4.示例3-添加多个列: ALTERTABLEemployees ADD(birth_dateDATE, join_dateDATE, salaryDECIMAL(10,2)); 在employees表中添加三个新列:birth_date、join_date和 salary...
ADD CONSTRAINT FK_DepartmentID FOREIGN KEY (Department_ID) REFERENCES Departments(ID); Conclusion Mastering the SQLALTERcommand empowers you to adapt your database structures to changing requirements without compromising data integrity. Whether you’re adding columns, altering data types, or managing co...
column_name data_type constraint; If we need to add various columns in the surviving table with the help of a single statement then the following syntax has been utilized, ALTER TABLE table_name ADD [COLUMN] column_definition, ADD [COLUMN] column_definition,…..; ...
Use the ADD CONSTRAINT clause to specify a primary key, foreign key, referential, unique, or check constraint on a new or existing column or on a set of columns.
There are known issues where the script processing may result in duplicate constraint and encryption key statements. If you encounter these issues, utilize the build output window to identify the source of the duplicates and manually remove them from the project. ...
PostgreSQL was originally named Postgres, referring to its origins as a successor to the Ingres database developed at the University of California, Berkeley. The 'SQL' was later added to emphasize its support for SQL. Footnotes Review thePrivacy Notices,Generative AI Prohibited Use Policy,Terms of...
Use theALTER TABLE ADDstatement to add one or more columns to an existing table. Syntax: Copy ALTERTABLE[schema_name.]table_nameADDcolumn_name1 data_typeconstraint,column_name2 data_typeconstraint...column_nameN data_typeconstraint; The following adds a new columnAddressof typevarcharand size ...