Luis,

L> Now, I have tried execute a single SQL
L> "select * from country" or
L> "select country,currency from country" without comillas
L> and report the error :
L> ISC ERROR CODE 335544652
L> "multiple rows in singleton selct"

L> Why ?????

if you tried that in the DSQL pane of IB_SQL, switch to the Cursor or
Query Form panes. DSQL is for singleton selects (that is, selects that
return at most one row) and other DML instructions.

You might want to use a more user-friendly tool while in your learning
process.

Ciao
--
Nando Dessena
mailto:nandod@...