alter table student add constraints pk_student_id PRIMARY key(id); 1. 1-9.插入原来的两条数据,报同样的错误 二、检查约束的三种方式 1.直接在创建表的字段后使用 check(条件) 例如 sage number(3) check(sage<150 and sage>0), 2.在创建表的语句的最后面使用 co
CREATE TABLE orders ( order_id integer PRIMARY KEY, product_no integer REFERENCES products, quantity integer ); # 定义多个 Column 组成的外键,要求被约束列(外键)的数量和类型应该匹配被引用列(主键)的数量和类型。 CREATE TABLE t1 ( a integer PRIMARY KEY, b integer, c integer, FOREIGN KEY (b, ...
cvarchar);altertabletbl_foreign_refdaddconstraintpk_tbl_foreign_refd_a_bprimarykey(a,b);createtabletbl_foreign( aint, bint, cvarchar);altertabletbl_foreignaddconstraintfk_tbl_foreign_a_bforeignkey(a,b)referencestbl_foreign_refd(a,b); 上表中完整外键其实如下,因为match,on delete,on update会...
constraint_type有四种:UNIQUE、PRIMARY KEY、CHECK、FOREIGN KEY 通过修改上边sql语句的table_name和constraint_type来进行相应的查询 警告
Support for PRIMARY KEY, FOREIGN KEY, indexes, and triggers on partitioned tables 本文以创建哈希分区表为例进行测试。 测试环境准备 创建分区表并插入测试数据,为后续测试做准备。 创建父表 CREATETABLEuserinfo ( userid int4, usernamecharactervarying(64), ...
is_active | boolean | not null | plain 8 | |falseIndexes:"table_name_pkey"PRIMARY KEY, btree (id) Foreign keys:"table_name_user_id_fkey"FOREIGN KEY (user_id) REFERENCES"users"(id) ON DELETE CASCADE ON UPDATE CASCADE Check constraints:"table_name_check_user_id"CHECK (user_id IS NOT...
格式1:在字段后添加primary key 格式2:使用constraint 约束名 primary key(字段名) create table cominfo( pno varchar2(32) primary key, pname varchar2(32), sex varchar2(6), birthday date, address varchar2(200), movephone number(18),
该表通过建立外部关键字(foreign key)链接生成,主要用来显示所需要查询的某部电影的相关信息: Create table "announcement" ( "id" Serial NOT NULL UNIQUE, "fid" integer NOT NULL Default 0, "cid" integer NOT NULL Default 0, PRIMARY KEY ("id") ); Alter table "announcement" add foreign key("...
WHEN'f'THEN'FOREIGN KEY' WHEN'p'THEN'PRIMARY KEY' WHEN'u'THEN'UNIQUE' ENDAS"constraint_type", CASEWHENc.condeferrable = 'f'THEN0 ELSE1 ENDASis_deferrable, CASEWHENc.condeferred = 'f'THEN0 ELSE1 ENDASis_deferred, t.relname AStable_name, ...
PostgreSQL foreign key constraint examples The following statements create the customers and contacts tables: DROP TABLE IF EXISTS customers; DROP TABLE IF EXISTS contacts; CREATE TABLE customers( customer_id INT GENERATED ALWAYS AS IDENTITY, customer_name VARCHAR(255) NOT NULL, PRIMARY KEY(customer_...