Updating columns by using a two-way assignment produces expected results because only the statement starting value of the column is accessed during statement execution. [Possibility of impact] Low
Updating columns by using a two-way assignment such as UPDATE T1 SET @v = column_name = can produce unexpected results because the live value of the variable can be used in other clauses such as the WHERE and ON clause during statement execution instead of the statement starting value. This can cause the meanings of the predicates to change unpredictably on a per-row basis. This behavior is applicable only when the compatibility level is set to 90.