<p>How do you randomly select a table row in T-SQL based on an applied weight for all candidate rows?</p>

<p>For example, I have a set of rows in a table weighted at 50, 25, and 25 (which adds up to 100 but does not need to), and I want to select one of them randomly with a statistical outcome equivalent to the respective weight.</p>

You simply need to sum the weights of all candidate rows, then choose a random point within that sum, then select the record that coordinates with that chosen point (each record is incrementally carrying an accumulating weight sum with it).
```
```
DECLARE @id int, @weight_sum int, @weight_point int
DECLARE @table TABLE (id int, weight int)

INSERT INTO @table(id, weight) VALUES(1, 50)
INSERT INTO @table(id, weight) VALUES(2, 25)
INSERT INTO @table(id, weight) VALUES(3, 25)

SELECT @weight_sum = SUM(weight)
FROM @table

SELECT @weight_point = ROUND(((@weight_sum - 1) * RAND() + 1), 0)

SELECT TOP 1 @id = t1.id
FROM @table t1, @table t2
WHERE t1.id >= t2.id
GROUP BY t1.id
HAVING SUM(t2.weight) >= @weight_point
ORDER BY t1.id

SELECT @id
```
```