T-SQL - get previous value How?

Question

Transact SQL

Hey!
There is a model field. How to write a code in t-sql, what function can be used to get the values ​​​​as in the parent_model field? That is, for each value of model, its parent value is needed.

thanks for any hints.

Answer 1

Use window functions LAG, LEAD:

SELECT model, LAG(model, 1,0) OVER (ORDER BY model ) as parent_model
FROM  [mytable]

1 - offset back,
0 - default value for the first value.
These options can be omitted.