How do I generate a random number for each row in a T-SQL select?

Take a look at SQL Server - Set based random numbers which has a very detailed explanation.

To summarize, the following code generates a random number between 0 and 13 inclusive with a uniform distribution:

ABS(CHECKSUM(NewId())) % 14

To change your range, just change the number at the end of the expression. Be extra careful if you need a range that includes both positive and negative numbers. If you do it wrong, it's possible to double-count the number 0.

A small warning for the math nuts in the room: there is a very slight bias in this code. CHECKSUM() results in numbers that are uniform across the entire range of the sql Int datatype, or at least as near so as my (the editor) testing can show. However, there will be some bias when CHECKSUM() produces a number at the very top end of that range. Any time you get a number between the maximum possible integer and the last exact multiple of the size of your desired range (14 in this case) before that maximum integer, those results are favored over the remaining portion of your range that cannot be produced from that last multiple of 14.

As an example, imagine the entire range of the Int type is only 19. 19 is the largest possible integer you can hold. When CHECKSUM() results in 14-19, these correspond to results 0-5. Those numbers would be heavily favored over 6-13, because CHECKSUM() is twice as likely to generate them. It's easier to demonstrate this visually. Below is the entire possible set of results for our imaginary integer range:

Checksum Integer: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Range Result:     0 1 2 3 4 5 6 7 8 9 10 11 12 13  0  1  2  3  4  5

You can see here that there are more chances to produce some numbers than others: bias. Thankfully, the actual range of the Int type is much larger... so much so that in most cases the bias is nearly undetectable. However, it is something to be aware of if you ever find yourself doing this for serious security code.

When called multiple times in a single batch, rand() returns the same number.

I'd suggest using convert(varbinary,newid()) as the seed argument:

SELECT table_name, 1.0 + floor(14 * RAND(convert(varbinary, newid()))) magic_number 
FROM information_schema.tables

newid() is guaranteed to return a different value each time it's called, even within the same batch, so using it as a seed will prompt rand() to give a different value each time.

Edited to get a random whole number from 1 to 14.

The Rand() function will generate the same random number, if used in a table SELECT query. Same applies if you use a seed to the Rand function. An alternative way to do it, is using this:

SELECT ABS(CAST(CAST(NEWID() AS VARBINARY) AS INT)) AS [RandomNumber]

Got the information from here, which explains the problem very well.

Do you have an integer value in each row that you could pass as a seed to the RAND function?

To get an integer between 1 and 14 I believe this would work:

FLOOR( RAND(<yourseed>) * 14) + 1

select round(rand(checksum(newid()))*(10)+20,2)

Here the random number will come in between 20 and 30. round will give two decimal place maximum.

If you want negative numbers you can do it with

select round(rand(checksum(newid()))*(10)-60,2)

Then the min value will be -60 and max will be -50.

If you don't need it to be an integer, but any random unique identifier, you can use newid()

SELECT table_name, newid() magic_number 
FROM information_schema.tables

try using a seed value in the RAND(seedInt). RAND() will only execute once per statement that is why you see the same number each time.

You would need to call RAND() for each row. Here is a good example

https://web.archive.org/web/20090216200320/http://dotnet.org.za/calmyourself/archive/2007/04/13/sql-rand-trap-same-value-per-row.aspx

It's as easy as:

DECLARE @rv FLOAT;
SELECT @rv = rand();

And this will put a random number between 0-99 into a table:

CREATE TABLE R
(
    Number int
)

DECLARE @rv FLOAT;
SELECT @rv = rand();

INSERT INTO dbo.R
(Number)
    values((@rv * 100));

SELECT * FROM R

Use newid()

select newid()

or possibly this

select binary_checksum(newid())

select ABS(CAST(CAST(NEWID() AS VARBINARY) AS INT)) as [Randomizer]

has always worked for me

If you want to generate a random number between 1 and 14 inclusive.

SELECT CONVERT(int, RAND() * (14 - 1) + 1)

OR

SELECT ABS(CHECKSUM(NewId())) % (14 -1) + 1

    DROP VIEW IF EXISTS vwGetNewNumber;
    GO
    Create View vwGetNewNumber
    as
    Select CAST(RAND(CHECKSUM(NEWID())) * 62 as INT) + 1 as NextID,
    'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'as alpha_num;

    ---------------CTDE_GENERATE_PUBLIC_KEY -----------------
    DROP FUNCTION IF EXISTS CTDE_GENERATE_PUBLIC_KEY;  
    GO
    create function CTDE_GENERATE_PUBLIC_KEY()
    RETURNS NVARCHAR(32)
    AS 
    BEGIN
        DECLARE @private_key NVARCHAR(32);
        set @private_key = dbo.CTDE_GENERATE_32_BIT_KEY();
        return @private_key;
    END;
    go

---------------CTDE_GENERATE_32_BIT_KEY -----------------
DROP FUNCTION IF EXISTS CTDE_GENERATE_32_BIT_KEY;  
GO
CREATE function CTDE_GENERATE_32_BIT_KEY()
RETURNS NVARCHAR(32)
AS 
BEGIN
    DECLARE @public_key NVARCHAR(32);
    DECLARE @alpha_num NVARCHAR(62);
    DECLARE @start_index INT = 0;
    DECLARE @i INT = 0;
    select top 1 @alpha_num = alpha_num from vwGetNewNumber;
        WHILE @i < 32
        BEGIN
          select top 1 @start_index = NextID from vwGetNewNumber;
          set @public_key = concat (substring(@alpha_num,@start_index,1),@public_key);
          set @i = @i + 1;
        END;
    return @public_key;
END;
    select dbo.CTDE_GENERATE_PUBLIC_KEY() public_key;

Update my_table set my_field = CEILING((RAND(CAST(NEWID() AS varbinary)) * 10))

Number between 1 and 10.

Try this:

SELECT RAND(convert(varbinary, newid()))*(b-a)+a magic_number 

Where a is the lower number and b is the upper number

If you need a specific number of random number you can use recursive CTE:

;WITH A AS (
        SELECT 1 X, RAND() R
    UNION ALL
        SELECT X + 1, RAND(R*100000) --Change the seed
        FROM A
        WHERE X < 1000 --How many random numbers you need
    )
SELECT
    X
    , RAND_BETWEEN_1_AND_14 = FLOOR(R * 14 + 1)
FROM A
OPTION (MAXRECURSION 0) --If you need more than 100 numbers