Ⅰ SQL Server有表A,表B，查询后立马更新数据 求大神帮忙
先按照公式，把a表中的数值计算出来，然后关联更新数据。
UPDATE B
SET B.aa = x.counts ,
B.bb = (case when x.counts >=10 and x.counts<20 then 4
when x.counts>=20 then 5
else null end )
FROM B
JOIN
(SELECT a.id,
SUM(CASE
WHEN a.aa IN (0, 1) THEN
2
WHEN a.aa IS NULL THEN
4
END) counts
FROM A GROUP BY id) x ON b.id = x.id
Ⅱ SQL 更新的同时做查询
那就关系到“锁”的问题了吧