合并结果合并所有SQL

Question

Table A:

Column1 | Column2
tableA01 | tableA11
tableA02 | tableA22

Table B:

Column1 | Column2
tableB01 | tableB11
tableB02 | tableB22

When sql using union all in these tables, the results like this:

SQL

SELECT * FROM tableA UNION ALL SELECT * FROM tableB

Result

Column1  | Column2
tableA01 | tableA11
tableA02 | tableA22
tableB01 | tableB11
tableB02 | tableB22

---

I ask: It possible merge the results?

I want the results somelike this:

Column1  | Column2
tableA01 | tableA11
tableB01 | tableB11
tableA02 | tableA22    
tableB02 | tableB22

Thanks!

Answer 1

Your result sets are the same, because result sets are unordered , unless you have an order by . Because your sample query doesn't have an order by , the two are equivalent.

More generally, though, you seem to want to interleave the values. You can do this using order by by doing:

select ab.*
from ((select a.*, (@rna := @rna + 1) as rn, 1 as which
       from a cross join (select @rna := 0) params
       order by <something>  -- You should order by something here so the ordering is well defined
      ) union all
      (select b.*, (@rnb := @rnb + 1) as rn, 2 as which
       from b cross join (select @rnb := 0) params
       order by <something>  -- You should order by something here so the ordering is well defined
      )
     ) ab
order by rn, which;

Answer 2

Simply order your unified results.

SELECT *
FROM (
    SELECT Column1, Column2 FROM tableA
    UNION ALL 
    SELECT Column1, Column2 FROM tableB
) Results 
ORDER BY Column1, Column2