How to Use Order by with Union All in SQL

How to use order by with union all in sql?

SELECT  * 
FROM 
        (
            SELECT * FROM TABLE_A 
            UNION ALL 
            SELECT * FROM TABLE_B
        ) dum
-- ORDER BY .....

but if you want to have all records from Table_A on the top of the result list, the you can add user define value which you can use for ordering,

SELECT  * 
FROM 
        (
            SELECT *, 1 sortby FROM TABLE_A 
            UNION ALL 
            SELECT *, 2 sortby FROM TABLE_B
        ) dum
ORDER   BY sortby 

Use ORDER BY with UNION ALL

SELECT * 
FROM 
(
  SELECT EventName, EventDate, 1 AS OrderPri, 
    ROW_NUMBER() OVER(ORDER BY EventDate) AS Row
  FROM EventTable 
  WHERE EventDate > GETDATE()
  UNION ALL
  SELECT EventName, EventDate, 2 AS OrderPri, 
    ROW_NUMBER() OVER(ORDER BY EventDate DESC) AS Row
  FROM EventTable 
  WHERE EventDate <= GETDATE()
) AS m
ORDER BY m.OrderPri, m.Row

SQL - How to Order By in UNION query

Put a UNION ALL in a derived table. To keep duplicate elimination, do select distinct and also add a NOT EXISTS to second select to avoid returning same person twice if found in both tables:

select name, surname
from
(
    select distinct name, surname, 1 as tno
    from table1
    union all
    select distinct name, surname, 2 as tno
    from table2 t2
    where not exists (select * from table1 t1
                      where t2.name = t1.name
                        and t2.surname = t1.surname)
) dt
order by tno, surname, name

How to ORDER BY one query only in a UNION ALL without subquery

The ORDER BY doesn't apply to just one SELECT, it applies to the whole result set, to the whole result after all rows are UNIONed. So, you need to include columns that will be used for sorting in each SELECT of the UNION ALL.

For example, the following is wrong syntax, because ORDER BY has to be after the last SELECT of the UNION.

SELECT CASE
           WHEN p.Category = 1
           THEN 'Very Active'
           WHEN p.Category = 2
           THEN 'Active '
           ELSE 'Departed'
       END AS Matrix
     , p.name AS [Name]
FROM #People p
ORDER BY p.Category

UNION ALL

SELECT 'Best Employee' AS Matrix
     , 'Alan' AS [Name]

Your second example from the question can be written in a simpler form, without sub-query:

SELECT CASE
           WHEN p.Category = 1
           THEN 'Very Active'
           WHEN p.Category = 2
           THEN 'Active '
           ELSE 'Departed'
       END AS Matrix
     , p.name AS [Name]
     , p.Category
FROM #People p

UNION ALL

SELECT 'Best Employee' AS Matrix
     , 'Alan' AS [Name]
     , NULL AS Category  --- or '' AS Category

ORDER BY Category;

In any case, the column Category has to be added in each SELECT statement of the UNION. I don't see how you can avoid it.

access-SQL-Query - Using Order By in UNION ALL

Try this:

SELECT table1.name, table1.age FROM table1
UNION ALL
SELECT table2.name, table2.age FROM table2
UNION ALL
SELECT table3.name, table3.age FROM table3 
ORDER BY 2;

You are ordering the results from your sub-queries, then joining these together into an unordered list. You need to move the ORDER BY to the end of the query.

As Damien says, you need to ORDER BY at the end of your query, otherwise you can't guarantee the results will always be what you want. Something like this should do the job:

SELECT name, age FROM (
    SELECT 1 AS table_order, table1.name, table1.age FROM table1
    UNION ALL
    SELECT 2 AS table_order, table2.name, table2.age FROM table2
    UNION ALL
    SELECT 3 AS table_order, table3.name, table3.age FROM table3 
) x
ORDER BY table_order, age;

How to use ORDER BY inside UNION

Something like this should work in MySQL:

SELECT a.*
  FROM ( 
         SELECT ...  FROM ... ORDER BY ... 
       ) a
 UNION ALL 
SELECT b.*
  FROM ( 
         SELECT ...  FROM ... ORDER BY ... 
       ) b

to return rows in an order we'd like them returned. i.e. MySQL seems to honor the ORDER BY clauses inside the inline views.

But, without an ORDER BY clause on the outermost query, the order that the rows are returned is not guaranteed.

If we need the rows returned in a particular sequence, we can include an ORDER BY on the outermost query. In a lot of use cases, we can just use an ORDER BY on the outermost query to satisfy the results.

But when we have a use case where we need all the rows from the first query returned before all the rows from the second query, one option is to include an extra discriminator column in each of the queries. For example, add ,'a' AS src in the first query, ,'b' AS src to the second query.

Then the outermost query could include ORDER BY src, name, to guarantee the sequence of the results.

---

FOLLOWUP

In your original query, the ORDER BY in your queries is discarded by the optimizer; since there is no ORDER BY applied to the outer query, MySQL is free to return the rows in whatever order it wants.

The "trick" in query in my answer (above) is dependent on behavior that may be specific to some versions of MySQL.

Test case:

populate tables

CREATE TABLE foo2 (id INT PRIMARY KEY, role VARCHAR(20)) ENGINE=InnoDB;
CREATE TABLE foo3 (id INT PRIMARY KEY, role VARCHAR(20)) ENGINE=InnoDB;

INSERT INTO foo2 (id, role) VALUES 
  (1,'sam'),(2,'frodo'),(3,'aragorn'),(4,'pippin'),(5,'gandalf');
INSERT INTO foo3 (id, role) VALUES 
  (1,'gimli'),(2,'boromir'),(3,'elron'),(4,'merry'),(5,'legolas');

query

SELECT a.*
  FROM ( SELECT s.id, s.role
           FROM foo2 s
          ORDER BY s.role
       ) a
 UNION ALL
SELECT b.*
  FROM ( SELECT t.id, t.role
           FROM foo3 t
          ORDER BY t.role
       ) b

resultset returned

    id  role     
 ------  ---------
      3  aragorn  
      2  frodo    
      5  gandalf  
      4  pippin   
      1  sam      
      2  boromir  
      3  elron    
      1  gimli    
      5  legolas  
      4  merry    

The rows from foo2 are returned "in order", followed by the rows from foo3, again, "in order".

Note (again) that this behavior is NOT guaranteed. (The behavior we observer is a side effect of how MySQL processes inline views (derived tables). This behavior may be different in versions after 5.5.)

If you need the rows returned in a particular order, then specify an ORDER BY clause for the outermost query. And that ordering will apply to the entire resultset.

As I mentioned earlier, if I needed the rows from the first query first, followed by the second query, I would include a "discriminator" column in each query, and then include the "discriminator" column in the ORDER BY clause. I would also do away with the inline views, and do something like this:

SELECT s.id, s.role, 's' AS src
  FROM foo2 s
 UNION ALL
SELECT t.id, t.role, 't' AS src
  FROM foo3 t
 ORDER BY src, role

Combining ORDER BY AND UNION in SQL Server

Put your order by and top statements into sub-queries:

select first.Id, first.Name 
from (
    select top 1 * 
    from Locations 
    order by Id) first
union all
select last.Id, last.Name 
from (
    select top 1 * 
    from Locations 
    order by Id desc) last

Using union and order by clause in mysql

You can do this by adding a pseudo-column named rank to each select, that you can sort by first, before sorting by your other criteria, e.g.:

select *
from (
    select 1 as Rank, id, add_date from Table 
    union all
    select 2 as Rank, id, add_date from Table where distance < 5
    union all
    select 3 as Rank, id, add_date from Table where distance between 5 and 15
) a
order by rank, id, add_date desc

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