Oracle parameterize finding column count of a table - ORA-00905: missing keyword

Question

I am adding a number of columns to multiple tables. Before I add them, I want to make sure they don't exist already.

SELECT count(*)
INTO myCount
FROM user_tab_cols
WHERE column_name = 'newCol'
  and table_name = 'tableName';

Since the only variables are the tableName and columnName, I thought of parameterizing these two variables hoping to reuse it. So I wrote a pl/sql:

DECLARE
 myCount      NUMBER;
 COUNT_COLUMN VARCHAR2(1000) :=
        ' SELECT count(*)
    INTO myCount
    FROM user_tab_cols
    WHERE column_name = :1
      and table_name = :2';


BEGIN

EXECUTE IMMEDIATE COUNT_COLUMN using 'columnName','tableName';
/*code to check count and add column*/

DBMS_OUTPUT.PUT_LINE(myCount);


EXCEPTION
    WHEN
        OTHERS THEN
        DBMS_OUTPUT.PUT_LINE( 'sql failed: ' || SQLCODE || ': ' || SUBSTR(SQLERRM, 1, 200));
END;

I expected the myCount variable to contain number of columns in a table. But I get the following error.

sql failed: -905: ORA-00905: missing keyword

How do I get rid of this error? what other ways do I have to achieve this?

Answer 1

INTO cluase must not be included in SQL query but to be used in EXECUTE IMMEDIATE statement. So, You need to fix your dynamic SQL as below -

DECLARE
 myCount      NUMBER;
 COUNT_COLUMN VARCHAR2(1000) :=
        ' SELECT count(*)
    FROM user_tab_cols
    WHERE column_name = :1
      and table_name = :2';

BEGIN            -- Add the BEGIN keyword to complete a PL/SQL block

EXECUTE IMMEDIATE COUNT_COLUMN INTO myCount using 'columnName','tableName';
/*code to check count and add column*/

DBMS_OUTPUT.PUT_LINE(myCount);


EXCEPTION
    WHEN
        OTHERS THEN
        DBMS_OUTPUT.PUT_LINE( 'sql failed: ' || SQLCODE || ': ' || SUBSTR(SQLERRM, 1, 200));
END;