SQL Server Copy Random data from one table to another

Question

I have 2 tables stuff and nonsense . nonsense is not the same size as stuff ; in this case it is has fewer rows, but it may have more.

The structures are something like this:

CREATE TABLE stuff (
    id INT PRIMARY KEY,
    details VARCHAR(MAX),
    data VARCHAR(MAX)
);

CREATE TABLE nonsense (
    id INT PRIMARY KEY,
    data VARCHAR(MAX)
);

The stuff table is already populated with details , but data is NULL for now.

I would like to copy data from one row of nonsense at random into each row of stuff . Since nonsense is smaller, there will naturally be duplicates, which is OK.

This does not work:

UPDATE stuff
SET data=(SELECT TOP 1 data FROM nonsense ORDER BY NewId());

Presumably the sub query is evaluated once before the rest of the query. However that's the sort of result I would have liked.

How do I achive this?

Answer 1

You need to correlate the sub-query to run it for each record.

UPDATE stuff
SET data=(SELECT TOP 1 data 
          FROM nonsense 
          where stuff.id = stuff.id  --here
          ORDER BY NewId());