ROBINSON PK_TB_CONS3_EMPNO_ENAME P TB_CONSTRAINT_3 ENABLED NOT DEFERRABLE VALIDATED ROBINSON SYS_C005554 U TB_CONSTRAINT_3 ENABLED NOT DEFERRABLE VALIDATED --两列上具有相同的约束名 SQL> SELECT * FROM user_cons_columns WHERE table_name = 'TB_CONSTRAINT_3'; OWNER CONSTRAINT_NAME TABLE_NAME ...
Assume we want to drop the UNIQUE constraint on the "Address" column, and the name of the constraint is "Con_First." To do this, we type in the following: MySQL: ALTER TABLE Customer DROP INDEX Con_First;Note that MySQL uses DROP INDEX for index-type constraints such as UNIQUE. ...
In Oracle, SQL Server, and Google BigQuery, the syntax for ALTER TABLE Drop Column is, ALTER TABLE "table_name" DROP COLUMN "column_name"; Let's look at the example. Assuming our starting point is the Customer table created in the CREATE TABLE section: Table Customer ...
We cannot remove this column until it has a dependent object in it. To remove this column, first, remove the dependency and then delete the column. 在此列中有从属对象之前,我们无法删除它。 要删除此列,请首先删除依赖项,然后删除该列。 ALTER TABLE [dbo].[ProductSales] DROP CONSTRAINT ck_price...
altertabletbaltercolumnidintnotnullaltertabletbaddconstraintpkidprimarykey(id) 4.删除主键 Declare@PkvarChar(100);Select@Pk=NamefromsysobjectswhereParent_Obj=OBJECT_ID('tb')andxtype='PK';if@Pkisnotnullexec('Alter table tb Drop'+@Pk)
Now we drop the IS_REGUAL column from the table, which has a default constraint as below. EXEC SP_HELP STUDENT_DETAILS SQL Copy Now if we drop the column by using the below query alter table STUDENT_DETAILS drop column IS_REGULAR SQL Copy Then we will face the below error. Now we ...
Then go back and delete the column. The same error is generated executing the T-SQL. -- attempt to drop column EmployeeStatusID from EmployeesALTERTABLE[dbo].[Employees]DROPCOLUMN[EmployeeStatusID]GO First, drop the key with an ALTER TABLE DROP CONSTRAINT and then drop the column with an ...
SQL>CREATETABLEtb_constraint_1 2( 3empno NUMBERPRIMARYKEY,--主键约束 4ename VARCHAR2(20)NOTNULL,--非空约束 5email VARCHAR2(60)UNIQUE,--唯一约束 6salNUMBER(5)CHECK(sal>1500),--核查约束 7deptno NUMBER(4)REFERENCEStb_dept(deptno)--外键约束 ...
[ CONSTRAINT constraint_name ] { [ NULL | NOT NULL ] { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] [ WITH FILLFACTOR = fillfactor ] [ WITH ( index_option [, ...n ] ) ] [ ON { partition_scheme_name (partition_column_name) | filegroup | "default" } ] | [ FOREIGN K...
该DROP INDEX语句不适用于通过定义PRIMARY KEY或UNIQUE约束创建的索引。 若要删除约束和相应的索引,请使用ALTER TABLE和DROP CONSTRAINT子句。 重要 将在SQL Server 的未来版本中删除定义的<drop_backward_compatible_index>语法。 请避免在新的开发工作中使用该功能,并考虑修改当前使用该功能的应用程序。 请改用在<dro...