Q:

How to separate from large table to two tables and combine the sub-table

For fast searching table , I need to separate a large table to two tables
example table:
+--------+--------+-------+------+
| source | target | count | prob |
+--------+--------+-------+------+
| test1  | test2  |     2 |    1 |
| cat    | dog    |     3 |   1.5|
| dog    | cat    |     1 |   0.5|
+--------+--------+-------+------+

Using the code below 
INSERT INTO Table2 (source,target,count,prob)
SELECT source,target,count,prob FROM Table1 WHERE count <2;

then delete originals
DELETE FROM Table1 WHERE count<2;

And count will grouping up after separating table in Table1, and new same element will increase after separating. 
For example:
source = 'dog' and target = 'cat' and count = 1 will be move to Table2 and Table1 will still grouping up like add the count or will be add new row source = 'dog' target ='cat' , count = 3.
How could I combine Table1 and Table2 (Table2 will not change after separating)

A:

You can combine the result with UNION
SELECT source, target, count, prob FROM tbl1

UNION

SELECT source, target, count, prob FROM tbl2

Just note there are lots of better ways to get better performance on large tables

