How to insert a row in mysql before union? - mysql

Question

Say I have the following:
CREATE TABLE newtable AS (
SELECT #rownum:=#rownum+1 as rownum, name, age FROM (
SELECT name, age FROM clubAmembers
UNION
SELECT name, age FROM clubBmembers
)
) AS atable
How can I make it such that I can "stick in a new row at the beginning of the table" prior to the SELECT union such that it would start with:
rownum | name| age
1 | "Jordan" | 6 <-- This is an arbitrarily inserted record with name="Jordan" age="6" that is not a part of any of the clubAmembers or clubBmembers table.
The rest of the table (rownum 2 and onwards) would contain the actual result form the union with clubAmembers then clubBmembers.
Basically I am looking for:
CREATE TABLE
INSERT a row "Jordan" | 6
Perform select with union such that the rows after the first would start with "rownum=2", all the data from clubAmembers, etc.
How to best do this?

Answer 1

"At the beginning of the table" is not truly meaningful to relational databases because the order results are returned are not guaranteed until you use an ORDER BY clause, at which point the order on disk becomes a moot point anyway.
In your case, since you want to guarantee an order in your result clause (and therefore ordering #rownum, you will have to use ORDER BY. Something like:
CREATE TABLE newtable AS (
SELECT #rownum:=#rownum+1 as rownum, name, age
FROM (
SELECT 'Jordan' AS name, 6 AS age, 0 AS ord
UNION
SELECT name, age, 1 AS ord FROM clubAmembers
UNION
SELECT name, age, 1 AS ord FROM clubBmembers
ORDER BY ord
)
) AS atable
Note that at no point does this guarantee that rows in clubAmembers will have a lower rownum than rows in clubBmembers. If you want to guarantee that clubAmembers have a lower rownum, while keeping the semantics of UNION (versus UNION ALL), you can use the following:
CREATE TABLE newtable AS (
SELECT #rownum:=#rownum+1 as rownum, name, age
FROM (
SELECT 'Jordan' AS name, 6 AS age, 0 AS ord
UNION ALL
SELECT name, age, 1 AS ord FROM clubAmembers
UNION ALL
SELECT name, age, 2 AS ord FROM clubBmembers AS b
WHERE NOT EXISTS(SELECT 1 FROM clubAmembers AS a
WHERE a.name = b.name AND a.age = b.age)
ORDER BY ord
)
) AS atable
Note if {name, age} could be duplicated within the clubXmembers table, you will need to add DISTINCT:
...
SELECT DISTINCT name, age, 1 AS ord FROM clubAmembers
UNION ALL
...
As per the request in the comments, if you had a clubCmembers table, you would do:
CREATE TABLE newtable AS (
SELECT #rownum:=#rownum+1 as rownum, name, age
FROM (
SELECT 'Jordan' AS name, 6 AS age, 0 AS ord
UNION ALL
SELECT name, age, 1 AS ord FROM clubAmembers
UNION ALL
SELECT name, age, 2 AS ord FROM clubBmembers AS b
WHERE NOT EXISTS(SELECT 1 FROM clubAmembers AS a
WHERE a.name = b.name AND a.age = b.age)
SELECT name, age, 3 AS ord FROM clubCmembers AS c
WHERE NOT EXISTS(SELECT 1 FROM clubAmembers AS a
WHERE a.name = c.name AND a.age = c.age)
AND NOT EXISTS(SELECT 1 FROM clubBmembers AS b
WHERE b.name = c.name AND b.age = c.age)
ORDER BY ord
)
) AS atable

Answer 2

I'm not sure if I got it right. But why don't you just add another union like this:
CREATE TABLE newtable AS (
SELECT #rownum:=#rownum+1 as rownum, name, age FROM (
SELECT 1, "Jordan", 6
UNION ALL
SELECT name, age FROM clubAmembers
UNION ALL
SELECT name, age FROM clubBmembers
)
) AS atable

Answer 3

You can separate the create table statmenet from the insert statmenet:
Create the table (you must know which colums are gona be there)
Insert your 1st record (INSERT INTO .... Values(...))
Use your statement but with insert into instead of create table like: INSERT INTO YourNewTable.... Values(YourSubQuery) (Nr and tye of columns must match your subquery)

Answer 4

This should do, I believe:
CREATE TABLE newtable AS (
SELECT (#rownum:=IFNULL(#rownum,0)+1)+1 as rownum, name, age FROM (
SELECT name, age FROM clubAmembers
UNION
SELECT name, age FROM clubBmembers
) AS s
UNION ALL
SELECT 1, 'Jordan', 6
) AS atable
Demo at SQL Fiddle: http://sqlfiddle.com/#!2/ab825/6