Automatic incremented ID, Sequence or Identity columns are those columns inwards whatever tabular array whose value is automatically incremented past times database based upon predefined rule. Almost all databases e.g. Microsoft SQL Server, MySQL, Oracle or Sybase supports motorcar incremented identity columns merely inwards dissimilar ways similar Oracle provides SEQUENCE object which tin dismiss hold out used to generate automatic numbers, Microsoft SQL Server upto 2008 version provides IDENTITY() functions for similar purpose. Sybase too has IDENTITY business office merely piffling dissimilar than SQL Server in addition to MySQL uses auto_incremented keyword to brand whatever numeric column auto incremented. As offset normal cast advised nearly top dog keys which is used to uniquely identity row in addition to if at that topographic point is no natural column or combination of column exists to act every bit primary key, generally database developer utilization motorcar incremented surrogate keys which is used to uniquely position each row. In this SQL tutorial nosotros volition come across how to generate motorcar incremented ID column inwards Microsoft SQL Server, Oracle 11g, MySQL in addition to Sybase ASE Server. By the agency this SQL article is continuation of my before post service on SQL in addition to database similar difference betwixt truncate in addition to delete inwards SQL in addition to Finding 2nd highest salary inwards MySQL in addition to SQL Server. If yous haven't got conduct chances to read them than I propose they are worth looking.
Auto incremented Id or sequence inwards SQL Server
SQL Server create got IDENTITY(seed, incremental value) business office which tin dismiss hold out used along amongst whatever column to brand that motorcar incremented id column. It takes ii parameter i is seed which is starting value in addition to other is incremental value which is used to generate adjacent number. default is IDENTITY(1,1) which generated sequential ids similar 1, 2, 3, 4 etc. Once yous brand whatever column every bit IDENTITY column yous don't require to furnish value for that in addition to it volition hold out automatically incremented in addition to inserted past times SQL Server. Here is the SQL Server question to generate IDENTITY columns:
DROP TABLE employee
CREATE TABLE employee (emp_id bigint IDENTITY(1,1) PRIMARY KEY NOT NULL, emp_name varchar(50) NULL, emp_phone bigint NULL)
INSERT INTO employee VALUES('Jack', 98434343)
INSERT INTO employee VALUES('Jill', 78434343)
INSERT INTO employee VALUES('Mack', 68434343)
SELECT * FROM employee
emp_id emp_name emp_phone
1 Jack 98434343
2 Jill 78434343
3 Mack 68434343
CREATE TABLE employee (emp_id bigint IDENTITY(1,1) PRIMARY KEY NOT NULL, emp_name varchar(50) NULL, emp_phone bigint NULL)
INSERT INTO employee VALUES('Jack', 98434343)
INSERT INTO employee VALUES('Jill', 78434343)
INSERT INTO employee VALUES('Mack', 68434343)
SELECT * FROM employee
emp_id emp_name emp_phone
1 Jack 98434343
2 Jill 78434343
3 Mack 68434343
SQL Server 2012 is going to back upwards SEQUENCE object, which tin dismiss too hold out used to create automatically incremented ids merely its non completely automatic in addition to acre inserting information yous require to telephone telephone sequence.next or something similar to populate adjacent value.
Auto incremented Id or sequence inwards Sybase
Sybase Adaptive Server or ASE too supports IDENTITY column merely amongst slightly dissimilar agency than SQL Server 2005 or 2008 e.g. it doesn't create got whatever IDENTITY() business office instead it create got IDENTITY keyword which tin dismiss hold out applied to whatever column acre creating tabular array using "create table" contention or "select into" contention every bit shown below:
CREATE TABLE employee (emp_id numeric(5,0) identity, emp_name varchar(50) NULL, emp_phone bigint NULL)
Here maximum value of identity is 10^5 -1 or 9999. Some of import points related to IDENTITY column inwards Sybase is :
1) One tabular array tin dismiss exclusively create got on IDENTITY column.
2) Similar to SQL Server, Sybase Adaptive Server too generates value of IDENTITY column automatically
3) Each row has unique value for identity column which tin dismiss hold out used to identity that row.
4) IDENTITY columns tin dismiss non hold out updated in addition to produce non allows nulls inwards Sybase database.
By the agency yous tin dismiss too create IDENTITY column past times modifying existing tabular array also.
Auto incremented Id or sequence inwards MySQL
MySQL database is completely dissimilar that SQL Server or Sybase Database merely it too supports concept of Identity column past times keyword AUTO_INCREMENT. AUTO_INCREMENT tin dismiss hold out used to uniquely position a row inwards a tabular array in addition to can hold out used to create primary key. mysql> CREATE TABLE customers (cust_id INT PRIMARY KEY AUTO_INCREMENT, cust_name VARCHAR (20), cust_phone INT);
Query OK, 0 rows affected (0.09 sec)
mysql> INSERT INTO customers(cust_name, cust_phone) VALUES ("Mitchell", 668332211);
Query OK, 1 row affected (0.02 sec)
mysql> INSERT INTO customers(cust_name, cust_phone) VALUES ("Rose", 98322365);
Query OK, 1 row affected (0.03 sec)
mysql> SELECT * FROM customers;
+---------+-----------+------------+
| cust_id | cust_name | cust_phone |
+---------+-----------+------------+
| 1 | Mitchell | 668332211 |
| 2 | Rose | 98322365 |
+---------+-----------+------------+
2 rows IN SET (0.00 sec)
Query OK, 0 rows affected (0.09 sec)
mysql> INSERT INTO customers(cust_name, cust_phone) VALUES ("Mitchell", 668332211);
Query OK, 1 row affected (0.02 sec)
mysql> INSERT INTO customers(cust_name, cust_phone) VALUES ("Rose", 98322365);
Query OK, 1 row affected (0.03 sec)
mysql> SELECT * FROM customers;
+---------+-----------+------------+
| cust_id | cust_name | cust_phone |
+---------+-----------+------------+
| 1 | Mitchell | 668332211 |
| 2 | Rose | 98322365 |
+---------+-----------+------------+
2 rows IN SET (0.00 sec)
Important points nearly AUTO INCREMENTED inwards MySQL
1) If yous don't specify value of AUTO_INCREMENT than mysql server automatically insert values every bit shown above.
2) Make certain yous utilization large plenty information type to concur value of automatically generated ids. e.g. if yous utilization TINYINT than maximum value of automatic id is 127.
3) You tin dismiss larn the terminal motorcar incremented id inwards mysql past times using business office LAST_INSERT_ID() .
Auto incremented Id or sequence inwards Oracle database
In Oracle 10g database yous tin dismiss utilization SEQUENCE to generate automatically increment unique values. In fellowship to utilization sequences yous offset require to create the SEQUENCE object inwards database in addition to thence acre inserting information into database yous require to utilization SEQUENCE.NEXTVAL to populate identity column.
CREATE TABLE Orders (order_id number(1), sum number(20))
INSERT INTO Orders(id_sequence.NEXTVAL, 200)
INSERT INTO Orders(id_sequence.NEXTVAL, 400)
INSERT INTO Orders(id_sequence.NEXTVAL, 200)
INSERT INTO Orders(id_sequence.NEXTVAL, 400)
That’s all on How to create motorcar incremented ID, identity column or sequence inwards Oracle, SQL Server, MySQL in addition to Sybase database. This is i of the primal concept inwards SQL in addition to it's e'er proficient to know how to create identity column inwards respective database yous are working.