表1:
jnh mc
1   m1
2   m2
3   m3

表2:
jnh mc
1   m3
2   m2
3   m1

表3:
jnh mc
1   
2   m2
3   

比较表1和表2,相同记录的mc值更新到表3,不同则为空.表1、表2、表3记录行相同。
谢谢!

VFP什么版本

v9.0

CREATE CURSOR t1 (jnh c(10), mc c(10))
INSERT INTO t1 VALUES ("1", "m1")
INSERT INTO t1 VALUES ("2", "m2")
INSERT INTO t1 VALUES ("3", "m3")
CREATE CURSOR t2 (jnh c(10), mc c(10))
INSERT INTO t2 VALUES ("1", "m3")
INSERT INTO t2 VALUES ("2", "m2")
INSERT INTO t2 VALUES ("3", "m1")
SELECT jnh, SPACE(10) mc FROM t1 INTO CURSOR t3 READWRITE
UPDATE t3 SET mc = tt.mc from (SELECT jnh, mc FROM t1 WHERE jnh + mc in (SELECT jnh + mc FROM t2)) tt WHERE t3.jnh == tt.jnh
SELECT t3
BROWSE

谢谢！
有两个问题请教：
１.jnh是数值型，提示“操作符/操作类型不符”，语句在何处更改？
２，需替换的字段多，应如何进行？
3，表3字段名与表1（表2）时，是一个已进的表，如下不
表3:
jnh mct
1   
2   m2
3   
应如何进行？

[此贴子已经被作者于2019-9-9 20:43编辑过]

CREATE CURSOR t1 (jnh I, mc c(10))
INSERT INTO t1 VALUES (1, "m1")
INSERT INTO t1 VALUES (2, "m2")
INSERT INTO t1 VALUES (3, "m3")
CREATE CURSOR t2 (jnh I, mc c(10))
INSERT INTO t2 VALUES (1, "m3")
INSERT INTO t2 VALUES (2, "m2")
INSERT INTO t2 VALUES (3, "m1")
CREATE CURSOR t3 (jnh I, mc c(10))
INSERT INTO t3 VALUES (1, "")
INSERT INTO t3 VALUES (2, "")
INSERT INTO t3 VALUES (3, "")

SET RELATION TO RECNO() INTO "t1", RECNO() INTO "t2"
REPLACE t3.mc WITH t1.mc ALL FOR t1.mc==t2.mc IN "t3"
BROWSE
RETURN

CREATE CURSOR t1 (jnh n(10), mc c(10))
INSERT INTO t1 VALUES (1, "m1")
INSERT INTO t1 VALUES (2, "m2")
INSERT INTO t1 VALUES (3, "m3")
CREATE CURSOR t2 (jnh n(10), mc c(10))
INSERT INTO t2 VALUES (1, "m3")
INSERT INTO t2 VALUES (2, "m2")
INSERT INTO t2 VALUES (3, "m1")
SELECT jnh, SPACE(10) mc FROM t1 INTO CURSOR t3 READWRITE
UPDATE t3 SET mc = tt.mc FROM (SELECT jnh, mc FROM t1 WHERE STR(jnh,10) + mc in (SELECT STR(jnh,10) + mc FROM t2)) tt WHERE t3.jnh == tt.jnh
SELECT t3
BROWSE


要想更好的解决问题，上传原始表

谢谢！

CLOSE DATABASES
USE 表1 IN 0 ALIAS b1
USE 表2 IN 0 ALIAS b2
USE 表3 IN 0 ALIAS b3
SELECT b3
SET RELATION TO RECNO() INTO  b1, RECNO() INTO b2
FOR i = 2 TO FCOUNT()
    BLANK ALL FIELDS (FIELD(i))
    REPLACE (FIELD(i)) WITH EVALUATE("b1." + FIELD(i, "b1")) FOR EVALUATE("b1." + FIELD(i, "b1")) == EVALUATE("b2." + FIELD(i, "b2"))
ENDFOR
SET RELATION TO
BROWSE

谢谢！