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 constraints ck_表名_字段名 check(条...
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...
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, ...
email | character varying(255) | not null | extended 76 | | 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 Che...
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), ...
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),
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_...
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, ...