Loop through records in PostgreSQL and generate guids? - database

I'm in the process of masking my ids from the url. I solved this by having a GUID in the URL instead of the primary key (which someone could easily guess). This GUID will map itself to the record just like a primary key.
Is this a decent solution? Someone would have to guess the GUID to see other people's data. Is there a security loophole I'm missing here.
How could I update my existing database to loop through records using PostgreSQL to update each record with a unique GUID?


You may also create the GUIDs without a Postgres extension, e. g.:
ALTER TABLE my_table ADD COLUMN guid UUID
DEFAULT MD5(RANDOM()::TEXT || ':' || CURRENT_TIMESTAMP)::UUID NOT NULL;
If you need not to define the GUID with a default value, you can use row data for the generation, the primary key for instance:
BEGIN;
ALTER TABLE my_table ADD COLUMN guid UUID;
UPDATE my_table SET guid = MD5(id::TEXT || ':' || CURRENT_TIMESTAMP)::UUID;
ALTER TABLE my_table ALTER guid SET NOT NULL;
END;


The uuid-ossp extension has functions for generating random uuids.
First:
create extension "uuid-ossp";
then:
alter table url add column guid uuid not null default uuid_generate_v4();

Related

how do you manage a database migration when you have to add a not null unique column to a table?

Consider a table like this one (postgresql):
create table t1 (
id serial not null primary key,
code1 int not null,
company_id int not null
);
create unique index idx1 on t1(code1, company_id);
I have to a new column code2 that will be not null and with a unique index like idx1, so the migration could be like:
alter table t1 add column code2 int not null;
create unique index idx2 on t1(code2, company_id);
The problem is: how do you manage the migration with the data that are already in the table?
You cannot apply this migration neither I can define a default value for the column.
What I was thinking to do is:
create and execute migration that just add the column without any constraint
insert the data manually in the column not with a migration
create and execute another migration that adds the constraints to the column
Is this a good practice or there are other ways?
As migration tool I am using flyway but I think it's the same for every database migration tool.

How do you add a unique primary key field automatically in SQL Server?

I am using SQL Server 2012 and need to add a column with a unique primary key. I am about to load several hundred thousand records BULK and just discovered repetition in the field I was going to use. Have seen SEQUENCE and GUID. Need some guidance on the best choice and how to go about setting this up so that the key field is populated during the bulk load.

When you create your table in which you want to insert information create an IDENTITY column. That will serve as an auto-populating column with a unique number for each record.
Here is a link that might help you.
If you have already created your table just change this query to what suits to your table name and run it in order to add the new column you requested.
ALTER TABLE mytable
ADD COLUMN unique_id IDENTITY (1,1)

Just a slight update on what’s already posted that includes details for adding primary key constraint
alter table database.schema.table_t
add ID_column int identity(1,1)
primary key (ID_column)
If you already set the primary key on this table just go and remove it before you execute this statement.

Insert a value in database

I am having a column named no. If I insert the no in database same no should not insert, if it is stored in that table. please help me.
Thank you

Make the required column unique using UNIQUE constraint.
Your create table statement should be like:
CREATE TABLE table_name ( col_1 datatype UNIQUE, col_2 datatype, .....)
This makes col_1 unique.

set it as Unique column and auto-increment.

A look on Google returns Sql learning Basics and this
You can set your column auto increment property to on it will enable the column to add a unique incremental value for each new record other way to is add a primary key or unique key constraint to that particular column
Thanks

Auto increment primary key in SQL Server Management Studio 2012

How do I auto increment the primary key in a SQL Server database table? I've had a look through the forum but can't see how to do this.
I've looked at the properties but can't see an option. I saw an answer where you go to the Identity specification property and set it to yes and set the Identity increment to 1, but that section is grayed out and I can't change the no to yes.
There must be a simple way to do this but I can't find it.

Make sure that the Key column's datatype is int and then setting identity manually, as image shows
Or just run this code
-- ID is the name of the [to be] identity column
ALTER TABLE [yourTable] DROP COLUMN ID
ALTER TABLE [yourTable] ADD ID INT IDENTITY(1,1)
the code will run, if ID is not the only column in the table
image reference fifo's

When you're creating the table, you can create an IDENTITY column as follows:
CREATE TABLE (
ID_column INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
...
);
The IDENTITY property will auto-increment the column up from number 1. (Note that the data type of the column has to be an integer.) If you want to add this to an existing column, use an ALTER TABLE command.
Edit:
Tested a bit, and I can't find a way to change the Identity properties via the Column Properties window for various tables. I guess if you want to make a column an identity column, you HAVE to use an ALTER TABLE command.

You have to expand the Identity section to expose increment and seed.
Edit: I assumed that you'd have an integer datatype, not char(10). Which is reasonable I'd say and valid when I posted this answer

Expand your database, expand your table right click on your table and select design from dropdown.
Now go Column properties below of it scroll down and find Identity Specification, expand it and you will find Is Identity make it Yes. Now choose Identity Increment right below of it give the value you want to increment in it.

CREATE TABLE Persons (
Personid int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.
In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record.
Tip: To specify that the "Personid" column should start at value 10 and increment by 5, change it to IDENTITY(10,5).
To insert a new record into the "Persons" table, we will NOT have to specify a value for the "Personid" column (a unique value will be added automatically):

Perhaps I'm missing something but why doesn't this work with the SEQUENCE object? Is this not what you're looking for?
Example:
CREATE SCHEMA blah.
GO
CREATE SEQUENCE blah.blahsequence
START WITH 1
INCREMENT BY 1
NO CYCLE;
CREATE TABLE blah.de_blah_blah
(numbers bigint PRIMARY KEY NOT NULL
......etc
When referencing the squence in say an INSERT command just use:
NEXT VALUE FOR blah.blahsequence
More information and options for SEQUENCE

When you're using Data Type: int you can select the row which you want to get autoincremented and go to the column properties tag. There you can set the identity to 'yes'. The starting value for autoincrement can also be edited there. Hope I could help ;)

I had this issue where I had already created the table and could not change it without dropping the table so what I did was:
(Not sure when they implemented this but had it in SQL 2016)
Right click on the table in the Object Explorer:
Script Table as > DROP And CREATE To > New Query Editor Window
Then do the edit to the script said by Josien; scroll to the bottom where the CREATE TABLE is, find your Primary Key and append IDENTITY(1,1) to the end before the comma. Run script.
The DROP and CREATE script was also helpful for me because of this issue. (Which the generated script handles.)

You can use the keyword IDENTITY as the data type to the column along with PRIMARY KEY constraint when creating the table.
ex:
StudentNumber IDENTITY(1,1) PRIMARY KEY
In here the first '1' means the starting value and the second '1' is the incrementing value.

If the table is already populated it is not possible to change a column to IDENTITY column or convert it to non IDENTITY column. You would need to export all the data out then you can change column type to IDENTITY or vice versa and then import data back.
I know it is painful process but I believe there is no alternative except for using sequence as mentioned in this post.

Be carefull like if you want the ID elements to be contigius or not. As SQLSERVER ID can jump by 1000 .
Examle: before restart ID=11
after restart , you insert new row in the table, then the id will be 1012.

You could do the following: New Table Creation:
-- create new table with Column ID which is Primary Key and Auto Increment --
CREATE TABLE titles(
id INT NOT NULL IDENTITY(1,1) PRIMARY KEY, --Primary Key with Auto-Increment --
keyword VARCHAR(260),
status VARCHAR(10),
);
If you Table Already exists and need to make the changes to ID column to be auto-increment and Primary key, then see below:
ALTER TABLE table DROP COLUMN id; // drop the existing ID in the table
ALTER TABLE table ADD id int IDENTITY(1, 1) NOT NULL; // add new column ID with auto-increment
ALTER TABLE table ADD CONSTRAINT PK_ident_test PRIMARY KEY CLUSTERED (id); // make it primary key

PostgreSQL No Auto Increment function?

I have a test application coded in Java for creating an indexed and non indexed table in a MySQL, PostgreSQL, Oracle and Firebird database (Amongst other things).
Is it simply a case that PostgreSQL doesnt allow the auto increment feature? If not, what is the normal procedure for having an indexed coloumn?
Thanks in advance

You may use SERIAL in PostgreSQL to generate auto increment field,
For eg:-
CREATE TABLE user (
userid SERIAL PRIMARY KEY,
username VARCHAR(16) UNIQUE NOT NULL
)
This will create userid as auto-increment primary key indexed.
If you don't want this as primary key, just remove PRIMARY KEY.

Use a column of type SERIAL. It works the same way as AUTOINCREMEMT on some other DBs. (Check the docs for other features you can use with it.)

With current Postgres, you can just use SERIAL for the column type.
With older versions of Postgres, you can implement this using SEQUENCE; the relevant procedure is:
CREATE SEQUENCE mytable_myid_seq;
ALTER TABLE mytable ALTER COLUMN myid SET DEFAULT NEXTVAL('mytable_myid_seq');
A good article on this is MySQL versus PostgreSQL: Adding an Auto-Increment Column to a Table

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