MySQL nested query won't run, runs on SQL Server - mysql

Question

I'm running multiple queries on both MySQL and SQLServer (same queries on both servers, same db). Almost all of them run fine. I have a problem with this one:
SELECT
`Extent1`.`IdGosc`,
`Extent2`.`Imie`,
`Extent2`.`Nazwisko`
FROM `TGosc` AS `Extent1`
INNER JOIN `TOsoba` AS `Extent2` ON `Extent1`.`IdGosc` = `Extent2`.`IdOsoba`
WHERE EXISTS(
SELECT 1 AS `C1`
FROM (
SELECT `Extent3`.`IdRezerwacja`
FROM `TRezerwacja` AS `Extent3`
(here!) WHERE `Extent1`.`IdGosc` = `Extent3`.`IdGosc`) AS `Project1`
)
It runs on SQL Server just fine, returns correct results, but MySQL says:
Error Code: 1054. Unknown column 'Extent1.IdGosc' in 'where clause'.
Why so? :|
Are there any limitations about MySQL nested queries?
(Please don't offer queries that return the same and work, I can do that as well, but it's not my point)

Answer 1

I have seen this problem on MySQL.
SELECT `Extent1`.`IdGosc`, `Extent2`.`Imie`, `Extent2`.`Nazwisko`
FROM `TGosc` `Extent1` INNER JOIN
`TOsoba` `Extent2`
ON `Extent1`.`IdGosc` = `Extent2`.`IdOsoba`
WHERE EXISTS (SELECT `Extent3`.`IdRezerwacja`
FROM `TRezerwacja` AS `Extent3`
(here!) WHERE `Extent1`.`IdGosc` = `Extent3`.`IdGosc`
)
Fortunately, in this case, you can just eliminate the middle subquery.

Answer 2

I too have faced this sort of error in mysql.What I have done at tht tym is :
mysql remember only current table so try to do it may b it would work
replace
FROM `TRezerwacja` AS `Extent3
with
FROM `TRezerwacja` AS `Extent3`,`TGosc` AS `Extent1`

Answer 3

Ok. It turns out to be the problem with MySQL.
I'm using Entity Framework's query, that later turns into db specific SQL. I this case MySQL. So, the query in EF is:
var query3a = from TGosc gosc in context.TGosc
where gosc.TRezerwacja
.Any(x => x.TPlatnosc
.Any(y => y.Kwota > 100000))
select new { gosc.IdGosc, gosc.TOsoba.Imie, gosc.TOsoba.Nazwisko };
Now, the provider in my app is Connector NET 6.7.4. It includes MySQL.Data and MySQL.Data.Entities, both in version 6.7.4.
However, I also installed MySQL for Visual Studio 1.0.2 to be able to use more GUI than code in Visual Studio. But this thing comes with same dlls, just in different (older) versions 6.6.5. And these took precedence over the newer ones when application was running. (It's weird in the first place that in the same MySQL Installer there are two somehow conflicting versions of the same dlls.)
Anyway, I removed MySQL for Visual Studio 1.0.2, which left me with the newer dlls and see what happens to the very same LINQ to Entities query, when it's being translated to db sql:
--old 6.6.5
SELECT
Extent1.IdGosc,
Extent2.Imie,
Extent2.Nazwisko
FROM TGosc AS Extent1
INNER JOIN TOsoba AS Extent2 ON Extent1.IdGosc = Extent2.IdOsoba
WHERE EXISTS(
SELECT 1 AS C1
FROM (
SELECT Extent3.IdRezerwacja
FROM TRezerwacja AS Extent3
WHERE Extent1.IdGosc = Extent3.IdGosc) AS Project1
WHERE EXISTS(
SELECT 1 AS C1
FROM TPlatnosc AS Extent4
WHERE (Project1.IdRezerwacja = Extent4.IdRezerwacja)
AND (Extent4.Kwota > 100000)))
vs
-- new 6.7.4
SELECT
Extent1.IdGosc,
Extent2.Imie,
Extent2.Nazwisko
FROM TGosc AS Extent1
INNER JOIN TOsoba AS Extent2 ON Extent1.IdGosc = Extent2.IdOsoba
WHERE EXISTS(
SELECT 1 AS C1
FROM TRezerwacja AS Project1
WHERE EXISTS(
SELECT 1 AS C1
FROM TPlatnosc AS Extent4
WHERE (Project1.IdRezerwacja = Extent4.IdRezerwacja)
AND (Extent4.Kwota > 100000))
AND Extent1.IdGosc = Project1.IdGosc)
It's similar to what Gordon Linoff answered in this post. The middle subquery dissapears.
And of course the new query works fine!
Summing up, I guess the MySQL provider for .NET got better over these versions. I still have some queries that cause similar problems but now I think I know why that is - provider. I'm ok with that.
The annoying thing is that there are two different versions of dlls, one overriding another, in MySQL Installer. I'm using mysql-installer-community-5.6.13.0.