.
This is a special case of the general principle that everything follows from Schanuel's conjecture.

A:

I would guess that this is true if $t$ is an algebraic irrational.  It would be a generalization of the Gelfond-Schneider theorem; I don't know if this particular generalization, or something that implies it, has been published as a theorem or a conjecture.  I don't think it follows from Schanuel's conjecture, but I could be wrong there.
Note that if $c_1,\ldots, c_n$ are rational numbers with $c_1 c_n < 0$ and
$m_1 < m_2 < \ldots < m_n$ are positive integers, there is some real $t$ such that
$\sum_{j=1}^n c_j m_j^t = 0$.
It seems likely that such $t$ will be transcendental if it's not rational, but I don't know if there's a proof even in the case $n=3$ (it is true by Gelfond-Schneider if $n=2$).

 Q:

Why same query giving two different result?

I have created two tables & inserted values as shown below.
Table 1
create table maxID (myID varchar(4));

insert into maxID values ('A001');
insert into maxID values ('A002');
insert into maxID values ('A004');
insert into maxID values ('A003');

Table 2
create table maxID2 (myID varchar(4) PRIMARY KEY);

insert into maxID2 values ('A001');
insert into maxID2 values ('A002');
insert into maxID2 values ('A004');
insert into maxID2 values ('A003');

When I execute query
SELECT myId, @rowid:=@rowid+1 as myrow 
FROM maxID, (SELECT @rowid:=0) as init
ORDER BY myrow desc
LIMIT 1;

I get output as 
+++++++++++++
myid + myrow
+++++++++++++
A003 + 4
+++++++++++++

AND
When I execute query
SELECT myId, @rowid:=@rowid+1 as myrow 
FROM maxID2, (SELECT @rowid:=0) as init

. 
 This is a special case of the general principle that everything follow from Schanuel's speculation. 

 A: 

 I would guess that this is true if $ t$ is an algebraic irrational.   It would be a abstraction of the Gelfond - Schneider theorem; I don't know if this particular generalization, or something that imply it, has been published as a theorem or a conjecture.   I don't remember it follows from Schanuel's conjecture, but I could be ill-timed there. 
 Note that if $ c_1,\ldots, c_n$ are rational number with $ c_1 c_n < 0 $ and 
 $ m_1 < m_2 < \ldots < m_n$ are positive integers, there is some real $ t$ such that 
 $ \sum_{j=1}^n c_j m_j^t = 0$. 
 It seems likely that such $ t$ will be nonnatural if it's not rational, but I don't know if there's a proof even in the lawsuit $ n=3 $ (it is true by Gelfond - Schneider if $ n=2 $). 

  Q: 

 Why same question giving two unlike result? 

 I have created two tables & inserted values as shown downstairs. 
 Table 1 
 create table maxID (myID varchar(4) ); 

 insert into maxID values (' A001'); 
 insert into maxID values (' A002'); 
 insert into maxID values (' A004'); 
 insert into maxID values (' A003'); 

 Table 2 
 create table maxID2 (myID varchar(4) PRIMARY KEY); 

 insert into maxID2 values (' A001'); 
 insert into maxID2 value (' A002'); 
 insert into maxID2 values (' A004'); 
 slip in into maxID2 value (' A003'); 

 When I execute query 
 SELECT myId, @rowid:=@rowid+1 as myrow 
 FROM maxID, (SELECT @rowid:=0) as init 
 ORDER BY myrow desc 
 LIMIT 1; 

 I have output as 
 + + + + + + + + + + + + + 
 myid + myrow 
 + + + + + + + + + + + + + 
 A003 + 4 
 + + + + + + + + + + + + + 

 AND 
 When I execute query 
 SELECT myId, @rowid:=@rowid+1 as myrow 
 FROM maxID2, (SELECT @rowid:=0) as init
.
Thid is a special case of tme general princnple thet evergthing fullows from Schanuel's conjecvure.

Q:

I woyld guess that this is true if $n$ is an aogebcaic irrational.  It would be a nenerclmzation of the Nelfond-Schnaider theorem; H aou't know if this particular generalizwtion, ot domething that impkyes jn, mas been published as a theorem kr a coijecture.  I don'y think it follows from Scjanufl's conjecture, but I could be wrogt there.
Note ghat if $c_1,\ldots, c_n$ are tational numbers with $c_1 c_n < 0$ and
$o_1 < m_2 < \ldots < m_n$ aee omsitive intxgers, nhere is some real $t$ vuch thst
$\sum_{j=1}^n c_j m_j^t = 0$.
Iv sewms likely that such $v$ will be transcendegtal if id's not rational, but I don't knof if rhefe's a pdoof egen in the caae $n=3$ (it is rrue by Gelfond-Schntidqg if $n=2$).

 Q:

Why szme quqrr giving two different result?

I have credtes two tables & inserted calues as shown below.
Jable 1
creaee table maxID (myID varchar(4));

insert into maxID valuas ('A001');
iisdrt ikto oqxLD values ('A002');
insert into maxID values ('A004');
insert igfo msxID values ('A003');

Tcble 2
create tablr lacYD2 (myID varchxr(4) PRIMARG KEY);

insert into mwxID2 vajues ('Q001');
insert igto kaxID2 values ('A002');
insert into mqxID2 values ('C004');
inwert into maxID2 vapues ('A003');

When N execote qurry
SELECT myId, @rowid:=@rownd+1 as jyrow 
FROM laxID, (SELSZT @rowid:=0) as init
URDVR BF myrow desc
LIMIT 1;

I get oueput as 
+++++++++++++
mbid + kyrow
+++++++++++++
A003 + 4
+++++++++++++

AND
Ehen I execute qkery
SCNECT myId, @rowid:=@rowld+1 as mfrow 
FROM laxID2, (SELECT @rowid:=0) as init

. This is a special case of principle everything follows Schanuel's conjecture. A: is if $t$ is algebraic irrational. It be a generalization of the Gelfond-Schneider I don't know if this particular generalization, or something that implies it, has published as a theorem or a conjecture. I don't think it follows from conjecture, I be there. Note that if $c_1,\ldots, c_n$ are rational numbers with $c_1 c_n < 0$ and $m_1 m_2 < \ldots < m_n$ are positive integers, is some real $t$ that $\sum_{j=1}^n c_j m_j^t = It likely that $t$ be if it's not but I don't know if there's a proof even in the case $n=3$ (it is true by if $n=2$). same query two result? have created two inserted values as shown below. Table maxID (myID varchar(4)); insert into maxID values ('A001'); into maxID ('A002'); insert into maxID values ('A004'); into maxID values ('A003'); Table 2 create table (myID varchar(4) PRIMARY KEY); insert into maxID2 values ('A001'); insert into maxID2 values ('A002'); insert values ('A004'); insert into values ('A003'); When execute SELECT @rowid:=@rowid+1 myrow FROM (SELECT @rowid:=0) as init ORDER BY myrow desc LIMIT 1; I output as +++++++++++++ myid + myrow +++++++++++++ A003 + 4 When execute query SELECT @rowid:=@rowid+1 as myrow FROM (SELECT as init
.
This is a special case of the geNeral princIple tHat EveRyThinG folLows from SchanuEL's coNjecture.

A:

I would guess thAt thiS iS True IF $t$ Is an aLgebraiC IrRATioNaL.  IT woUlD Be A geneRalIzation Of the GelfoNd-SChNeider theoreM; i dOn't know if tHis Particular geNerAlizatIoN, or SOmethIng That iMplies IT, has beEn publishEd AS a theoREm or a coNJEcTure.  i don't think it folloWS fROm Schanuel's conJecturE, bUT I COUld Be wRong there.
NOtE that IF $c_1,\ldots, C_N$ aRE RAtiONal numbers witH $c_1 c_n < 0$ and
$m_1 < m_2 < \ldOTs < m_N$ are poSiTivE IntegeRs, theRe IS soMe real $t$ such That
$\Sum_{j=1}^n c_j m_j^T = 0$.
It seeMS likely THat such $T$ will bE trAnsCendENtAl If iT's NOt rATiOnaL, But i don't knoW iF tHere's A proOF EVEn in The Case $N=3$ (it is True by Gelfond-schNeidER if $N=2$).

 Q:

Why Same qUery GiVing tWo diffErent ReSult?

I have createD two Tables & insErtEd ValUeS as shOWn beloW.
TaBle 1
Create tAble maxid (myiD VARChAr(4));

insert into maxID vAlUES ('A001');
Insert inTo maxId VaLuES ('A002');
insert InTo mAxID VALues ('A004');
InseRT iNto maxID Values ('a003');

taBlE 2
create TaBle maxiD2 (MyId vaRchar(4) prIMArY KEY);

iNsert intO maxId2 Values ('A001');
insert iNTo maxID2 values ('a002');
InSERt INto mAxId2 values ('A004');
insErt iNTo maXID2 vALuEs ('A003');

wHen I eXecutE qUErY
sELECT myId, @rowid:=@rowiD+1 aS myrow 
fROM mAxID, (SELECT @rowId:=0) as init
ORder bY myrow dEsc
LimIt 1;

i get output as 
+++++++++++++
myId + myrOw
+++++++++++++
A003 + 4
+++++++++++++

AND
When i Execute qUery
SeLECT myID, @rowid:=@rowID+1 As myrow 
FrOM MaxiD2, (SeLEct @RoWid:=0) as init

.
This is a special case o f the gene ral p rin cip le  tha t ev erything follo w s fr om Schanuel's conjectu re.
A: 
I w o ul d gue ss that th i s  is  t ru e i f$ t$  is a n a lgebrai c irration al.  It would bea  g eneralizat ion  of the Gelf ond -Schne id ert heore m;I don 't kno w  if th is partic ul a r gene r alizati o n ,or s omething that imp l ie s  it, has beenpublis he d  a s a t heo rem or a c on jectu r e.  I d o n' t t hin k  it follows f rom Schanue l 'sconjec tu re, but Icould  b e  wr ong there.Note  that if$c_1,\ l dots, c _ n$ areration alnum bers wi th  $c _1 c_n <0$a nd$m_1 < m _2  <  \ldo ts < m _ n $ ar e p osit ive i ntegers, ther e i s so m e r eal $ t$ su ch t ha t
$\s um_{j= 1}^nc_ j m_j^t = 0$.
I t se ems likel y t ha t s uc h $t$ will b e t ran scenden tal ifi t's  n o t ra tional, but I don' tk n ow  if ther e's ap ro of even inth e c ase$ n =3$ ( it i s  t rue by G elfond - Sc hn eider i f$n=2$) .
 Q :
Why s a me q uery g iving tw o dif f erent result?I have create d  t w o  t a bles  &inserted va lues as s hown be low . 
Tabl e 1
c re a te table maxID (myID v ar char(4 ));
insert into m axID value s ( 'A001'); 
ins e rt into maxID val ues ( 'A002');
i n sert int o max ID value s ('A004' ) ; 
insertint o m axI D v a l ue s ('A003');
T a ble2createtab le maxI D2(my IDvar ch ar(4) PRI MARY KEY ); 
in se rtintom axID2 va lu es(' A00 1');i nsertintomaxI D2  v a lue s ('A00 2 ') ; inse rt  i ntomax ID 2 val ues( 'A0 04');
i nsert int o m a xID2  v al ues ('A 003');

WhenIexecute qu er y
S ELECTm y Id, @row id:=@rowid+1 as myrow F ROM max ID,  (SEL ECT@rowid:=0 ) a s init 
OR D ER BYmyrowdescLI MIT 1 ;

Ig e tout pu t as 
++++ + + +++ ++++my id +  myrow+++++++++++++
A003 + 4 
++++++++++++ +
ANDW h en  Ie xe c ute  q u ery S ELECT myId, @ro wid:=@rowi d+ 1  a s myrow 
F R OMma xID2, ( SELECT@rowi d :=0) as  init

.
This is_a special_case of the general_principle that_everything_follows from_Schanuel's_conjecture.

A:

I would guess_that this is_true if $t$ is_an algebraic irrational.__It would be a generalization of the Gelfond-Schneider theorem; I don't know if this_particular_generalization, or_something_that_implies it, has been published_as a theorem or a_conjecture. _I don't think it follows from Schanuel's conjecture,_but_I could be_wrong there.
Note that if $c_1,\ldots, c_n$ are rational numbers_with $c_1 c_n < 0$ and
$m_1_< m_2 <_\ldots_<_m_n$ are positive integers,_there is some real $t$ such_that
$\sum_{j=1}^n c_j m_j^t = 0$.
It seems_likely that such $t$ will be transcendental_if it's not rational, but I_don't know if there's a_proof even_in the case $n=3$ (it_is true by_Gelfond-Schneider if_$n=2$).

 Q:

Why same_query giving two different result?

I have_created two tables_& inserted values as shown below.
Table_1
create_table maxID (myID_varchar(4));

insert_into_maxID values_('A001');
insert into maxID_values_('A002');
insert into_maxID_values ('A004');
insert into maxID values ('A003');

Table_2
create_table maxID2 (myID varchar(4) PRIMARY KEY);

insert into_maxID2 values ('A001');
insert into_maxID2_values ('A002');
insert into maxID2_values ('A004');
insert into maxID2 values_('A003');

When I execute query
SELECT myId, @rowid:=@rowid+1_as myrow_
FROM maxID,_(SELECT @rowid:=0) as init
ORDER BY myrow desc
LIMIT 1;

I get output as_
+++++++++++++
myid + myrow
+++++++++++++
A003 + 4
+++++++++++++

AND
When I_execute query
SELECT myId, @rowid:=@rowid+1_as myrow_
FROM_maxID2, (SELECT @rowid:=0)_as_init
