Oracle: execute immediate multiple statements - oracle

Question

I need to create columns on multiple tables as well as indexes, I need to catch first if columns already exist as to ignore for the multiple executes, is the following the correct way of handling a single exeption for multiple columns adds executes?
----------------------------------
-- Alter column null --
----------------------------------
DECLARE
col_allready_exists EXCEPTION;
PRAGMA EXCEPTION_INIT(col_allready_exists, -01430);
BEGIN
execute immediate 'ALTER TABLE XtkEnumValue ADD iOrder NUMBER(20) DEFAULT 0';
execute immediate 'ALTER TABLE XtkReport ADD iDisabled NUMBER(3) DEFAULT 0';
execute immediate 'ALTER TABLE XtkWorkflow ADD iDisabled NUMBER(3) DEFAULT 0';
execute immediate 'ALTER TABLE XtkRights ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
execute immediate 'ALTER TABLE NmsSeedMember ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
execute immediate 'ALTER TABLE NmsTrackingUrl ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
/
----------------------------------
-- Index creation --
----------------------------------
DECLARE
already_exists EXCEPTION;
columns_indexed EXCEPTION;
PRAGMA EXCEPTION_INIT ( already_exists, -955 );
PRAGMA EXCEPTION_INIT (columns_indexed, -1408);
BEGIN
EXECUTE IMMEDIATE 'CREATE INDEX XTKRIGHTS_TSLASTMODIFIED_IDX ON XTKRIGHTS(tsLastModified)';
EXECUTE IMMEDIATE 'CREATE INDEX ER_TSLASTMODIFIED_IDX_CC057ED6 ON NmsSeedMember(tsLastModified)';
EXECUTE IMMEDIATE 'CREATE INDEX RL_TSLASTMODIFIED_IDX_E5F04BF5 ON NmsTrackingUrl(tsLastModified)';
EXCEPTION
WHEN already_exists OR columns_indexed THEN
dbms_output.put_line('Index already exists, skipping...');
END;
/
Update
Is the following also correct?
DECLARE
allready_null EXCEPTION;
object_allready_exists EXCEPTION;
PRAGMA EXCEPTION_INIT(allready_null, -01442);
PRAGMA EXCEPTION_INIT(object_allready_exists, -955);
BEGIN
execute immediate 'ALTER TABLE NMSACTIVECONTACT MODIFY (ISOURCEID NULL)';
execute immediate 'CREATE TABLE NMSACTIVECONTACT_CPY as SELECT * FROM NMSACTIVECONTACT where 1=0';
EXCEPTION
WHEN allready_null THEN
dbms_output.put_line('ISOURCEID is already null, skipping...');
WHEN object_allready_exists THEN
dbms_output.put_line('NMSACTIVECONTACT_CPY already exists, continuing...');
END;
/

Answer 1

No, catch the exception for each column. If you don't then it may fail on the first column and then it will skip all the remaining statements as the exception handling block is processed.
DECLARE
col_allready_exists EXCEPTION;
PRAGMA EXCEPTION_INIT(col_allready_exists, -01430);
BEGIN
BEGIN
execute immediate 'ALTER TABLE XtkEnumValue ADD iOrder NUMBER(20) DEFAULT 0';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
BEGIN
execute immediate 'ALTER TABLE XtkReport ADD iDisabled NUMBER(3) DEFAULT 0';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
BEGIN
execute immediate 'ALTER TABLE XtkWorkflow ADD iDisabled NUMBER(3) DEFAULT 0';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
BEGIN
execute immediate 'ALTER TABLE XtkRights ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
BEGIN
execute immediate 'ALTER TABLE NmsSeedMember ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
BEGIN
execute immediate 'ALTER TABLE NmsTrackingUrl ADD tsLastModified TIMESTAMP(6) WITH TIME ZONE';
EXCEPTION
WHEN col_allready_exists THEN
dbms_output.put_line('Already exists, skipping...');
END;
END;
/

Answer 2

I normally put the DDL and exception handling into a procedure and call that for each column to be added:
declare
procedure add_column
( p_table_name user_tab_columns.table_name%type
, p_column_name user_tab_columns.column_name%type
, p_column_spec varchar2 )
as
column_already_exists exception;
pragma exception_init(column_already_exists, -1430);
k_ddl constant long :=
'alter table '||p_table_name||' add '||p_column_name||' '||p_column_spec;
begin
execute immediate k_ddl;
dbms_output.put_line(p_table_name||'.'||p_column_name||' added');
exception
when column_already_exists then
dbms_output.put_line(p_table_name||'.'||p_column_name||' already exists, skipping...');
when others then
raise_application_error(-20000, 'Command failed: '||k_ddl, true);
end;
begin
add_column('XtkEnumValue', 'iOrder', 'number(20) default 0');
add_column('XtkReport', 'iDisabled', 'number(3) default 0');
add_column('XtkWorkflow', 'iDisabled', 'number(3) default 0');
add_column('XtkRights', 'tsLastModified','timestamp(6) with time zone');
add_column('NmsSeedMember', 'tsLastModified','timestamp(6) with time zone');
add_column('NmsTrackingUrl','tsLastModified','timestamp(6) with time zone');
end;
You could use similar logic for modifying columns, adding indexes etc.
If I was adding the same columns to multiple tables, I might construct a cursor For loop using a Cartesian product to generate all the table/column combinations and and a minus to subtract the ones that already exist in user_tab_columns.