You’re looking for is called an IDENTITY column: create table student ( sid integer not null GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1) ,sname varchar(30) ,PRIMARY KEY (sid) ); A sequence is another option for doing this, but you need to determine which one is proper for your particular situation. Read this … Read more
Yes, you can do it like this: for (char alphabet=”A”; alphabet <= ‘Z’; alphabet++) { System.out.println(alphabet); } It is also possible with typecasting: for (int i = 65; i <= 90; i++) { System.out.println((char)i); }
Check out a nice answer about Sequence vs. Serial. Sequence will just create sequence of unique numbers. It’s not a datatype. It is a sequence. For example: create sequence testing1; select nextval(‘testing1’); — 1 select nextval(‘testing1’); — 2 You can use the same sequence in multiple places like this: create sequence testing1; create table table1(id … Read more
To use AUTO_INCREMENT you need to deifne column as INT or floating-point types, not CHAR. AUTO_INCREMENT use only unsigned value, so it’s good to use UNSIGNED as well; CREATE TABLE discussion_topics ( topic_id INT NOT NULL unsigned AUTO_INCREMENT, project_id char(36) NOT NULL, topic_subject VARCHAR(255) NOT NULL, topic_content TEXT default NULL, date_created DATETIME NOT NULL, date_last_post … Read more
You can have an auto-Incrementing column that is not the PRIMARY KEY, as long as there is an index (key) on it: CREATE TABLE members ( id int(11) UNSIGNED NOT NULL AUTO_INCREMENT, memberid VARCHAR( 30 ) NOT NULL , `time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , firstname VARCHAR( 50 ) NULL , lastname VARCHAR( 50 … Read more
The reason this feels weird to you is that you are thinking of the increment on the counter as part of the insert operation, and therefore the “DO NOTHING” ought to mean “don’t increment anything”. You’re picturing this: Check values to insert against constraint If duplicate detected, abort Increment sequence Insert data But in fact, … Read more
I strongly disagree with author of selected answer that No auto-increment id in MongoDB and there are good reasons. We don’t know reasons why 10gen didn’t encourage usage of auto-incremented IDs. It’s speculation. I think 10gen made this choice because it’s just easier to ensure uniqueness of 12-byte IDs in clustered environment. It’s default solution … Read more
From DBCC CHECKIDENT DBCC CHECKIDENT ( table_name, RESEED, new_reseed_value ) If no rows have been inserted to the table since it was created, or all rows have been removed by using the TRUNCATE TABLE statement, the first row inserted after you run DBCC CHECKIDENT uses new_reseed_value as the identity. Otherwise, the next row inserted uses … Read more
Changing the IDENTITY property is really a metadata only change. But to update the metadata directly requires starting the instance in single user mode and messing around with some columns in sys.syscolpars and is undocumented/unsupported and not something I would recommend or will give any additional details about. For people coming across this answer on … Read more
For some databases, you can just explicitly insert a NULL into the auto_increment column: INSERT INTO table_name VALUES (NULL, ‘my name’, ‘my group’)