为其他列中的每个唯一值分配新值

你也可以使用 apply :

select t.*, t1.Col2
from table t outer apply
     ( select count(*) as Col2
       from table t1
       where t1.id <= t.id and t1.col1 = 'TARGET.'
     ) t1;

然而,累加和也是一种很好的方法。

SELECT *, SUM(CASE WHEN Col1 = 'Target' THEN 1 ELSE 0 END ) OVER (ORDER BY Id) FROM @a

SUM(..) OVER (ORDER BY .. ) 相等 SUM(...) OVER (ORDER BY .. ROWS UNBOUNDED PRECEDING AND CURRENT ROW)

OVER Clause