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...
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...
Chris Saxon is an Oracle Developer Advocate for SQL. His job is to help you get the best out of the Oracle Database and have fun with SQL! To help you with this he blogs atAll Things SQL. He also creates videos combining SQL and magic on YouTube at theThe Magic of SQL. If you ...
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...
和约束 SQL参考 系统 系统概述 系统视图 V3.x与 V4.x 视图 SYS 租户视图 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_DIRECTORIES ALL_...
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; ...
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; ...
SQL 参考 视图 系统视图概述 系统视图 3.x 4.x 视图变更 SYS 租户系统 MySQL 租户系统 Oracle 租户系统 字典视图 ALLALL_TABLES ALL_ARGUMENTS ALLCOL_COMMENTSALL_COLL_TYPES ALL_COL_PRIVS ALLCONSTRAINTS _CONS_COLUMNS ALL_DEF_AUDIT_ ALL_ERRORS _INDEXES ALL_INDCOLUMNS ALLIND_EXPRESSIONS...
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...