PLS-00103 creating an external table with dynamic SQL - oracle

Question

I'm trying to dynamically create an external table but I'm getting error message PLS-00103: Encountered the symbol "EXTERNAL". I'm also using ora_hash in the external table definition; please let me know it is the right way to get the ora_hash value.
create or replace procedure CHECKTABLEEXIST1 (p_tab_name in varchar2,DATAFILE in varchar2) --user_tables.table_name%type)
is
tab_name varchar2(100) := p_tab_name;
n Number(3);
ext_table varchar(100) := tab_name|| ' as select * from xyz WHERE 1=0';
begin
select count(*) into n from tab where TName=upper(tab_name);
--dbms_output.put_line(n);
if n=0 then
execute immediate 'create table ' || ext_table ;
else
execute immediate 'drop table ' || tab_name;
execute immediate 'create table ' || ext_table;
ORGANIZATION EXTERNAL
(
TYPE ORACLE_LOADER
DEFAULT DIRECTORY DE_DUBFILE
ACCESS PARAMETER
(
RECORDS DELIMITED BY NEWLINE
CHARACTERSET US7ASCII
BADFILE 'UPLOAD':'p_tab_name.bad'
DISCARDFILE 'UPLOAD':'p_tab_name.dis'
LOGFILE 'UPLOAD':'p_tab_name.log'
FILEDS TERMINATED BY ','
optionally enclosed by '"'
TRAILING NULLCOLS
MISSING FIELD VALUES ARE NULL
(
t1 ,t2,t3,t4,t5 date "YYYYMMDD" ,t6,t7,
t8 ,t9 ,
DETL_CLMNS_HASH "ORA_HASH( :t4||:t7 )",
KEY_CLMNS_HASH "ORA_HASH(:t1||:t2||:t5)", t10,t11)
)
LOCATION (DATAFILE)
);
end if;
end;
I'm getting error message :
LINE/COL ERROR
-------- -----------------------------------------------------------------
16/14 PLS-00103: Encountered the symbol "EXTERNAL" when expecting one o
f the following:
:= . ( # % ;

Answer 1

Everything from ORGANIZATION onwards is being seen as PL/SQL code, not part of your dynamic SQL statement. You're appending the table name to the create table but then not appending the rest as part of that statement string. You need to do something like:
execute immediate 'create table ' || p_tab_name || '
( /* put column names and types here */ )
ORGANIZATION EXTERNAL
(
TYPE ORACLE_LOADER
DEFAULT DIRECTORY DE_DUBFILE
ACCESS PARAMETERS
(
RECORDS DELIMITED BY NEWLINE
CHARACTERSET US7ASCII
BADFILE UPLOAD:''' || p_tab_name || '.bad''
DISCARDFILE UPLOAD:''' || p_tab_name || '.dis''
LOGFILE UPLOAD:''' || p_tab_name || '.log''
FIELDS TERMINATED BY '',''
optionally enclosed by ''"''
MISSING FIELD VALUES ARE NULL
(
t1 ,t2,t3,t4,t5 date mask "YYYYMMDD" ,t6,t7,
t8 ,t9, t10,t11
)
LOCATION (''' || DATAFILE || ''')
)';
In the first line the terminating semicolon has been replaced with concatenation of a new string literal. The references to variables p_tab_name and DATAFILE have to be broken out from that literal too, requiring more single quotes and concatenation; and the single quotes that are actually part of the statement need to be escaped by doubling them up. There were various other quotes missing as well. What's shown should now run.
I've also change the table name being used to just p_tab_name, but you need to specify the column names and data types explicitly. It doesn't make sense to use as select * ... for an external table. That isn't legal syntax, either before organization or after the rest if the current statement. I suppose you could extract that information from all_tab_columns and build that part dynamically too, but if you're basing it on a fixed table you ought to know those anyway.
Your logic for dropping/creating is off too - I think you just want:
if n>0 then
execute immediate 'drop table ' || p_tab_name;
end if;
execute immediate 'create table ' || p_tab_name || '
...
... so you don't have to repeat the create statement in both branches.
I've also corrected a couple of other mistakes; PARAMETERS rather then PARAMETER; FIELDS rather then FILEDS; removed TRAILING NULLCOLS. Try to execite the command as static SQL before converting it to dynamic. There may still be other issues.
And I've removed the last two calculated columns:
DETL_CLMNS_HASH "ORA_HASH( :t4||:t7 )",
KEY_CLMNS_HASH "ORA_HASH(:t1||:t2||:t5)")
The ORACLE_LOADER driver doesn't allow manipulations like that; SQL*Loader does but they are not exactly the same. You also can't define virtual columns on an external table. If you're using this as a staging table to load data into another (real) table then you can calculate those hashes during the transfer; otherwise you can create a view over this external table which includes the calculated columns.