V4MD problem with a query

[info at vallemediatime.com]

Hi Ruslan,
the fc15 resolve NULL value problems, good.

Today I don't understand because this simple query give me bad result, 

query = "SELECT RecID, * from" && gTableName && "WHERE \
(myFld> 0) AND (myFld<= '" & searchString & "') " 
gCursor = gDb.sqlSelect(query, #kServer, gLockType, #kRandom)

I try to explain you
myFld is a  field of table STUDENTI.createStringField("myFld", 3)

in 3 record of table STUDENTI I  I type: 030, 048, 167 into myFld

if I insert 170 in my searchField and launch the query I get
030
048
167 
OK

and if I insert 160 I get
030
048
OK

nut if I insert 1 or 001 ...I get
030
048
NOT OK

and if I insert 2  or 002 ...I get
030
048
167
NOT OK

Why?
Thanks Paolo