performanceINT(11)DEFAULTNULL, salaryFLOATDEFAULTNULL,PRIMARYKEY (emp_id),CONSTRAINTfk_performanceFOREIGNKEY (performance)REFERENCESmerits (performance) );-- insert data for merits tableINSERTINTOmerits(performance,percentage)VALUES(1,0), (2,0.01), (3,0.03), (4,0.05), (5,0.08);-- insert data ...
使用Transact-SQL 对INSERT 和 UPDATE 语句禁用外键约束 在“对象资源管理器”中,连接到 数据库引擎的实例。 在标准栏上,选择“新建查询” 。 将以下示例复制并粘贴到查询窗口中,然后选择“执行”。 SQL USEAdventureWorks2022; GOALTERTABLEPurchasing.PurchaseOrderHeaderNOCHECKCONSTRAINTFK_PurchaseOrderHeader_Employee...
和INSERT一样,对于每一个索引,SQL Server都会从跟节点向下直到找到叶子节点。当找到叶子节点之后,SQL Server可能会马上删除这条数据,也可能不马上删除,而是在页中的标志位设置这页已经被删除。这种逻辑上被删除但物理上还存在术语称为:虚影记录(GHOST Record),在接下来合适的时机,SQL Server才会删除虚影记录,我将在...
方式1:使用SQL语句进行查询,结果更加详细。 --运行“执行计划”: explain plan for SQL语句; explain plan for select * from dual; --查询“执行计划”结果(固定语句) select * from table(dbms_xplan.display()); 1. 2. 3. 4. 方式2:使用PL/SQL Dev 工具提供"执行计划窗口"进行查询,内容相对而言少一...
CONSTRAINT fk_performance FOREIGN KEY (performance) REFERENCES merits (performance) ); -- insert data for merits table INSERT INTO merits(performance,percentage) VALUES(1,0), (2,0.01), (3,0.03), (4,0.05), (5,0.08); -- insert data for employees table ...
使用Transact-SQL 若要停用 INSERT 和 UPDATE 陳述式的檢查條件約束 在物件總管中,連線到資料庫引擎的一個執行個體。 在標準列上,按一下 [新增查詢]。 將下列範例複製並貼入查詢視窗中,然後按一下 [執行]。 SQL 複製 USE AdventureWorks2022; GO ALTER TABLE Purchasing.PurchaseOrderHeader ...
USE AdventureWorks2022; GO BEGIN TRANSACTION; BEGIN TRY -- Intentionally generate a constraint violation error. UPDATE HumanResources.Department SET Name = N'MyNewName' WHERE DepartmentID BETWEEN 1 AND 2; END TRY BEGIN CATCH SELECT ERROR_NUMBER() AS ErrorNumber ,ERROR_SEVERITY() AS ErrorSeverit...
USE AdventureWorks2022; GO BEGIN TRANSACTION; BEGIN TRY -- Intentionally generate a constraint violation error. UPDATE HumanResources.Department SET Name = N'MyNewName' WHERE DepartmentID BETWEEN 1 AND 2; END TRY BEGIN CATCH SELECT ERROR_NUMBER() AS ErrorNumber ,ERROR_SEVERITY() AS ErrorSeverit...
CONSTRAINT FKEmpPer FOREIGN KEY (SSN) REFERENCES Person (SSN) ) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 下面的视图使用某个人的两个表中的所有相关数据建立报表。 复制 CREATE VIEW Employee AS SELECT P.SSN as SSN, Name, Address, ...
If an update to a row violates a constraint or rule, violates the NULL setting for the column, or the new value is an incompatible data type, the statement is canceled, an error is returned, and no records are updated. When an UPDATE statement encounters an arithmetic error (overflow, div...