mysql实用技巧之比较两个表是否有不同数据的方法分析

SELECT t1.pk, t1.c1
FROM t1
UNION ALL
SELECT t2.pk, t2.c1
FROM t2

CREATE TABLE t1(
 id int auto_increment primary key,
  title varchar(255) 
);
CREATE TABLE t2(
 id int auto_increment primary key,
  title varchar(255),
  note varchar(255)
);

INSERT INTO t1(title)
VALUES('row 1'),('row 2'),('row 3');

INSERT INTO t2(title)
VALUES('row 1'),('row 2'),('row 3');

SELECT id,title
FROM (
  SELECT id, title FROM t1
  UNION ALL
  SELECT id,title FROM t2
) tbl
GROUP BY id, title
HAVING count(*) = 1
ORDER BY id;

INSERT INTO t2(title,note)
VALUES('new row 4','new');

mysql> SELECT id,title
FROM (
  SELECT id, title FROM t1
  UNION ALL
  SELECT id,title FROM t2
) tbl
GROUP BY id, title
HAVING count(*) = 1
ORDER BY id;
+----+-----------+
| id | title   |
+----+-----------+
| 4 | new row 4 |
+----+-----------+
1 row in set