checking if table exists function - sql

Question

Can you help me rectify this block of code plz?
`CREATE OR REPLACE FUNCTION TABLE_EXISTS(name VARCHAR(50))
RETURNS BOOLEAN
AS
BEGIN
DECLARE counttable INTEGER;
SELECT COUNT(1) INTO counttable FROM USER_TABLES WHERE TABLE_NAME=name;
if counttable=0 then
return false
else
return true
end if;
END;
/
IF (TABLE_EXISTS("LEADS_DELETED")) then
DROP TABLE LEADS_DELETED;
end if;
/
CREATE GLOBAL TEMPORARY TABLE LEADS_DELETED
(
ID NUMBER(19),
PRIMARY KEY (ID)
) ON COMMIT DELETE ROWS`

Answer 1

You can use a construct like this when you want to create or recreate a table (try to drop and catch the ORA-00942 exception that gets thrown when the object doesn't exist):
DECLARE
table_does_not_exist exception;
pragma exception_init(table_does_not_exist, -942);
BEGIN
EXECUTE IMMEDIATE 'DROP TABLE LEADS_DELETED';
EXCEPTION
WHEN table_does_not_exist THEN
NULL;
END;
/
CREATE TABLE ...

Answer 2

You have double quotes aroung your table name "LEADS_DELETED" should be 'LEADS_DELETED'.
I'd also wrap the table_name in your query with UPPER(table_name) too.
You also need to put the DROP TABLE command inside an EXECUTE IMMEDIATE wrapper.
You declare your variable in the wrog place too, it needs to be declared before the BEGIN clause.
CREATE OR REPLACE
FUNCTION TABLE_EXISTS(name VARCHAR(50))
RETURNS BOOLEAN
AS
counttable INTEGER;
BEGIN
SELECT COUNT(1)
INTO counttable
FROM USER_TABLES
WHERE TABLE_NAME=UPPER(name);
if counttable=0
then
return false
else
return true
end if;
END;
/
-- I suggest you use a bind variable instead of the literal table name.
IF TABLE_EXISTS('LEADS_DELETED')
THEN
EXECUTE IMMEDIATE 'DROP TABLE LEADS_DELETED';
END IF;
/
-- Could be
IF table_exists(v_table_name)
THEN
EXECUTE IMMEDIATE 'DROP TABLE :tablename'
USING v_table_name;
END IF;