在Oracle数据库中,"GENERATED BY DEFAULT AS IDENTITY"是一个用于自动生成唯一标识符的特性,通常用于主键字段。以下是对该特性的详细解释和示例: 1. 解释Oracle中的"GENERATED BY DEFAULT AS IDENTITY"的含义 "GENERATED BY DEFAULT AS IDENTITY"是Oracle 12c及更高版本中引入的一个特性,它允许数据库为表中的特定列...
GENERATED ALWAYS AS IDENTITY不能在该列中插入NULL值 GENERATED ALWAYS AS IDENTITY不能指定具体值插入 GENERATED ALWAYS AS IDENTITY 不能使用update更新该列 2.2 BY DEFAULT选项 DROPTABLEidentity_test_tab PURGE;CREATETABLEidentity_test_tab ( idNUMBERGENERATEDBYDEFAULTASIDENTITY, descriptionVARCHAR2(30) ); 插入...
createtabletb_test ( id number GENERATED ALWAYSASIDENTITY, name varchar2(100) ); 此时试图插入指定ID字段的元组将报错,因为ID字段总是自动生成的,例如,执行下述语句: INSERTINTOTB_TESTVALUES(1,'Zyon'); 将报: ORA-32795: 无法插入到“始终生成”身份列 2. GENERATED BY DEFAULT AS IDENTITY createtablet...
方式一:Identity Columns新特性自增该种方式要求Oracle版本≥12c在自增字段后使用以下2种语句的1种:generated by default as IDENTITYgenerated always as identity建表语句:CREATE TABLE userinfo ( id number(11) generated by default as IDENTITY,--使用自增功能 name varchar2(20) , age number(3)) 测试:...
1、在创建表时使用 GENERATED BY DEFAULT AS IDENTITY 语法来创建自增长的列。 obclient [oboracle]>CREATETABLECtable ( ->IDNUMBERGENERATEDBYDEFAULTASIDENTITYMINVALUE1MAXVALUE999999INCREMENTBY1STARTWITH1primarykey, ->NAMEVARCHAR2(480), -> AGENUMBER(10,0) ...
id1 number generated by default as identity , name varchar2(10) ); Table created. SQL> insert into tab_sql_idnty4(name) values (‘name1’); 1 row created. commit SQL> insert into tab_sql_idnty4 values (NULL,‘name1’);
总体而言,GENERATED BY DEFAULT AS IDENTITY 属性创建(方案二)的序列不如自定义序列(方案一)好用。 总结 本文验证并阐述了在 OB Oracle 中实现自增主键的两种方法:创建自定义序列和利用 GENERATED BY DEFAULT AS IDENTITY 属性生成序列。 方案一 创建自定义序列的时,需要为每张有自增列的表创建一个单独的序列,序...
CREATE TABLE persons( person_id NUMBER GENERATED BY DEFAULT AS IDENTITY, first_name VARCHAR2(50) NOT NULL, last_name VARCHAR2(50) NOT NULL, PRIMARY KEY(person_id) ); INSERT INTO "C##DBUSER"."PERSONS" VALUES ('1', 'zhang', 'feng'); INSERT INTO "C##DBUSER"."PERSONS" VALUES...
(event_id) ); -- SALE table create table sale ( sale_id number(*,0) generated by default on null as identity, sheep_id varchar2(6) not null, price number(*,2) not null, sale_date date not null, location varchar2(45) not null, note varchar2(4000), constraint sale_pk primary ...
account_id NUMBER GENERATEDBYDEFAULTASIDENTITY, first_name VARCHAR2(25)NOTNULL, last_name VARCHAR2(25)NOTNULL, email VARCHAR2(100), phone VARCHAR2(12) , full_name VARCHAR2(51) GENERATED ALWAYSAS( first_name||' '||last_name ),PRIMARYKEY(account_id) ...