Add records randomly between select result - mysql

Question

I want to add records randomly in select result like this example:
1 a
2 a
- b
3 a
- b
4 a
5 a
6 a
- b
7 a
8 a
- b
In a simple query I select from a table but in this case I want result mix with b table without random a result otherwise I simply could union them and then order random().
EDIT:
-- ----------------------------
-- Table structure for t1
-- ----------------------------
DROP TABLE IF EXISTS `t1`;
CREATE TABLE `t1` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;
INSERT INTO `t1` VALUES ('1', 'a');
INSERT INTO `t1` VALUES ('2', 'a');
INSERT INTO `t1` VALUES ('3', 'a');
INSERT INTO `t1` VALUES ('4', 'a');
INSERT INTO `t1` VALUES ('5', 'a');
INSERT INTO `t1` VALUES ('6', 'a');
INSERT INTO `t1` VALUES ('7', 'a');
INSERT INTO `t1` VALUES ('8', 'a');
INSERT INTO `t1` VALUES ('9', 'a');
INSERT INTO `t1` VALUES ('10', 'a');
-- ----------------------------
-- Table structure for t2
-- ----------------------------
DROP TABLE IF EXISTS `t2`;
CREATE TABLE `t2` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
INSERT INTO `t2` VALUES ('1', 'b');
INSERT INTO `t2` VALUES ('2', 'b');
INSERT INTO `t2` VALUES ('3', 'b');
So I can union two tables and then order by random and the result will be like this:
SELECT
t1.ID,
t1.name
FROM
t1
UNION ALL
SELECT
t2.ID,
t2.name
FROM
t2
ORDER BY RAND();
5 a
2 a
6 a
3 a
7 a
2 b
9 a
1 a
10 a
3 b
4 a
8 a
1 b
But I don't want to random records I just only want mix two tables records like first example.
I hope my question is now clear.

Answer 1

I don't think pure SQL is the best solution here, I would do it in some end framework (I don't know what you use), like PHP, Delphi, Java, etc. This way is more easier and you can control it better. But if you would like to do it in SQL, here an idea:
SET #max_t1 = (SELECT MAX(ID) FROM t1);
SET #max_t2 = (SELECT MAX(ID) FROM t2);
SET #last_order = RAND()*#max_t1/#max_t2;
SELECT
t1.ID, t1.name, t1.ID AS "Ord"
FROM
t1
UNION ALL
SELECT
t2.ID, t2.name, #last_order:=#last_order+RAND()*#max_t1/#max_t2
FROM
t2
ORDER BY Ord
This way we generate a random position for TableB, then in every row we add some random value to it, in according to the size differency between the two tables, then order the whole result on this column.