sql>alter table Goods modify GoodsId not null; (2)增加身份证也不能重复 sql>alter table Customers add constraint UQ_CardId unique(CardId); (3)增加客户的住址只能是海淀、朝阳、东城、西域 sql>alter table Customers add constraint CK_Address check(Address in ('海淀','朝阳','东城','西域'));...
Learn how to use SQL triggers to automate tasks, maintain data integrity, and enhance database performance. Try practical examples like the CREATE, ALTER, and DROP commands in MySQL and Oracle. Oluseye Jeremiah 13 Min. Lernprogramm SQL Query Examples and Tutorial If you are looking to get...
To alter a table already created in MySQL, SQL Server, Oracle, or MS Access use the following SQL: ALTER TABLE Orders ADD FOREIGN KEY (P_Id) REFERENCES Persons(P_Id) CHECK Constraint The CHECK constraint ensures that all values in a column satisfy certain conditions. This is your checks a...
和约束 SQL参考 PL参考 系统 系统概述系统视图总览 V3.x V4.x 视图变更 SYS 租户系统视图 MySQL租户系统 Oracle租户视图 字典 ALL_ALL_ ALL_ARGUMENTS _COL_COMMENTS _COL_PRIVS ALL_COLLTYPES ALL_CONS_COLUMNS ALLCONSTRAINTS ALLDB_LINKS ALLDEF_AUDIT_OPTS _DEPENDENCIES ALL_...
You can't alter the criteria for a constraint in Oracle Database. To change it you must drop and recreate the constraint. Learn how to do this process online for check constraints, not null, unique constraints, primary keys, and foreign keys.
関連項目: TO_DATEファンクションは、『Oracle Database SQL言語リファレンス』および『Oracle Database開発ガイド』を参照。 RELY VARCHAR2(4) VALIDATED = NOT VALIDATEDの場合、この列は、クエリー・リライトのときに制約が考慮されるか(RELY)されないか(NULL)を示す。 VALIDATED = VALIDATED...
query to find unique constraints on a table in oracle SQL> CREATE TABLE DEPT_MASTER ( dept_nr NUMBER UNIQUE, dept_name varchar2(100) NOT NULL, dept_status NUMBER(1,0) NOT NULL, created_at date ); Table created. SQL> select CONSTRAINT_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints...
To create a FOREIGN KEY constraint in PostgreSQL, use the same ANSI SQL syntax as in Oracle. You can create a foreign key constraint in-line or out-of-line during table creation.Use the REFERENCES clause to specify the table referenced by the foreign key constraint....
SQL> drop table t; drop table t * ERROR at line 1: ORA-02449: unique/primary keys in table referenced by foreign keys (违反了constraint,员工销售表t1有參照到table t,这个reference relation不允许你drop table t) SQL> drop table t cascade constraints; ...
INTO Persons IN 'Backup.mdb' FROM Persons 类似的拷贝还可以使用:create table back_table as select * from source_table; 6. SQL 约束 约束用于限制加入表的数据的类型。 可以在创建表时规定约束(通过 CREATE TABLE 语句),或者在表创建之后也可以(通过 ALTER TABLE 语句)。