Before Oracle 12c, we don’t have a direct method of generating an AUTO_INCREMENT column in a table. We need to use the combination of Sequences and Triggers. Now, we have two different ways to implement it. Using IDENTITY column There are three options on IDENTITY COLUMN BY DEFAULT ...
Use trigger to create autoincrement column : Before Insert Trigger « Trigger « Oracle PL / SQL
http://stackoverflow.com/questions/11296361/how-to-create-id-with-auto-increment-on-oracle There is no such thing as "auto_increment" or "identity" columns in Oracle. However, you can model it easily with a sequence and a trigger: Table definition: CREATE TABLE departments ( ID NUMBER(10)...
INCREMENT BY int_value指定序列的自增步数。int_value不可以为 0。 如果指定为正数,则序列为升序;如果指定为负数,则序列为降序。 不指定时缺省值为 1。 CACHE int_value指定在内存中预分配的自增值个数,int_value默认为 20。CACHE int_value的值必须大于 1,如果CACHE INT_VALUE的值为 1,则等价于NOCACHE。
column_definition|[,|[CONSTRAINT[constraint_name]]{PRIMARYKEY|UNIQUE}(column_name)//在创建所有列后添加约束|[CONSTRAINT[constraint_name]]FOREIGNKEY(column_name,column_name...)references_clause constraint_state|[CONSTRAINT[constraint_name]]CHECK(expression)constraint_state]column_definition_list: column_...
(a); 374 375 移除列 c: 376 377 mysql> ALTER TABLE t2 DROP COLUMN c; 378 379 添加一个名为 c 的 AUTO_INCREMENT 整型列: 380 381 mysql> ALTER TABLE t2 ADD c INT UNSIGNED NOT NULL AUTO_INCREMENT, 382 ADD INDEX (c); 383 384 注意,我们索引了 c,因为 AUTO_INCREMENT 列必须被索引,同样...
CREATE TABLE users ( id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(255) NOT NULL, email VARCHAR(255) UNIQUE NOT NULL, age INT CHECK (age >= 0) ); 参考链接 MySQL CREATE TABLE 文档 SQL 语法错误解决 通过以上信息,您可以更好地理解CREATE TABLE语句的基础概念、优势、类型和应用场景,并解决常见...
[AUTO_INCREMENT]43[PRIMARY KEY][reference_definition]44orPRIMARYKEY(index_col_name,...)45orKEY[index_name](index_col_name,...)46orINDEX[index_name](index_col_name,...)47orUNIQUE[INDEX][index_name](index_col_name,...)48orFULLTEXT[INDEX][index_name](index_col_name,...)49or[...
在Oracle中,用如下SQL命令创立了一种序列:CREATE SEQUENCE my_seqSTART WITH 394INCREMENT BY 12NOMINVALUENOMAXVALUENOCYCLENOCACHE;顾客执行涉及my_seq.NEXTVAL旳SQL语句三次,然后执行涉及my_seq.CURRVAL旳SQL语句四次,请问序列my_seq旳目前值是(选一项) 答案 B 解析 null 本题来源 题目:在Oracle中,用如下SQL命...
| cust_id |int(11) | NO | PRI | NULL | auto_increment | | cust_name |char(50) | NO | | NULL | | | cust_address |char(50) | YES | | NULL | | | cust_city |char(50) | YES | | NULL | | | cust_state |char(5) | YES | | NULL | | ...