Can one table have two identity columns in SQL Server? - sql

Question

I am trying to make two columns auto increment but this column shows an error [user_id] as id + 0 PRIMARY KEY NOT NULL saying
Only UNIQUE or PRIMARY KEY constraints can be created on computed columns
What I am trying to do is, if id = 1, make user_id= 1 as well.
CREATE TABLE [dbo.TBL_TXN_USER]
(
[id] int NOT NULL IDENTITY(1,1),
[user_id] as id + 0 PRIMARY KEY NOT NULL ,
[username] varchar(150) NOT NULL,
[fullname] varchar(150) NOT NUll,
[pwd] varchar(50) NOT NUll,
[email] varchar(150) NOT NULL,
[mobile] varchar(150) NOT NULL,
[designation] varchar(150) NOT NULL,
[deleted] int NULL,
[created_date] datetime NULL,
[creator_user_id] int NULL,
[changed_date] datetime NULL,
[changer_user_id] int NULL,
[add_content] int NULL,
[edit_content] int NULL,
[delete_content] int NULL,
[manage_user] int NULL,
[view_log] int NULL,
)
What is wrong in [user_id]? How to solve it?

Answer 1

the error message is because you put the NOT NULL constraint on the computed column.
on sql server 2012 the complete error message is:
Only UNIQUE or PRIMARY KEY constraints can be created on computed
columns, while CHECK, FOREIGN KEY, and NOT NULL constraints require
that computed columns be persisted.
here is a working script (i changed the table name):
CREATE TABLE dbo.[TBL_TXN_USER]
(
[id] int NOT NULL IDENTITY(1,1),
[user_id] as id + 0 persisted not null primary key,
[username] varchar(150) NOT NULL,
[fullname] varchar(150) NOT NUll,
[pwd] varchar(50) NOT NUll,
[email] varchar(150) NOT NULL,
[mobile] varchar(150) NOT NULL,
[designation] varchar(150) NOT NULL,
[deleted] int NULL,
[created_date] datetime NULL,
[creator_user_id] int NULL,
[changed_date] datetime NULL,
[changer_user_id] int NULL,
[add_content] int NULL,
[edit_content] int NULL,
[delete_content] int NULL,
[manage_user] int NULL,
[view_log] int NULL,
);
GO
i have a couple of comments about that question .
- a calculated field with a fixed formula with static values as primary key instead of the id itself is a waste of resources: one of the 2 fields should not be there
- a field with the name of a system function (user_id) is something i would avoid at all costs.
- the question looks like an attempt to put in place a solution (the calculated field as id) for an hidden issue.

Answer 2

Sorry for my misunderstanding, So you want to add auto increments two column in one table. Actually that is not accept at SQL-server so I am going to give you another option below
CREATE TRIGGER [dbo].[insert_triger] ON [dbo].[TBL_TXN_USER]
FOR INSERT
AS
update TBL_TXN_USER set [user_id] = id
where id = (
select MAX(id)
from TBL_TXN_USER
)

Answer 3

column aliases work with select statement not create table, also for [user_id] you didn't provide any data type.
Use the following to create your table :
CREATE TABLE [dbo.TBL_TXN_USER](
[id] int NOT NULL IDENTITY(1,1),
[user_id] int PRIMARY KEY NOT NULL ,
....rest of code
To update [user_id] consider using a trigger.