sql语句问题

[mackly]

我想把一个表中的一个字段通过一个条件更新到另一表的一个字段中去
这样的sql语句错在那
UPDATE usra01
SET usra01.c0105 =
(SELECT max(usr01.档案号)
FROM usr01
WHERE usr01.入厂证号 = usra01.z0108)
FROM usra01
为什么更新后的字段有一些以前不为空的他复为了null

[gmlxf]

UPDATE a
SET a.c0105 =
(SELECT max(档案号)
FROM usr01
WHERE 入厂证号 = a.z0108 group by 档案号)
FROM usra01 a

[dlpseeyou]

UPDATE usra01
SET usra01.c0105 =
(SELECT max(usr01.档案号)
FROM usr01
WHERE usr01.入厂证号 = usra01.z0108) tb

[victorycyz]

UPDATE usra01
SET c0105 =b.maxno
FROM usra01 a join
( SELECT 入厂证号, max(usr01.档案号) as maxno
FROM usr01
group by 入厂证号
) b
on b.入厂证号 = a.z0108

[gmlxf]

更正：
UPDATE a
SET a.c0105 =
(SELECT max(档案号)
FROM usr01
WHERE 入厂证号 = a.z0108 group by 入厂证号)
FROM usra01 a

[wzh1215]

UPDATE usra01
SET c0105 =b.maxno
FROM
( SELECT 入厂证号, max(usr01.档案号) as maxno
FROM usr01
group by 入厂证号
) b
on b.入厂证号 = usra01.z0108