Oracle: Declare multiple constants and use them in WHERE clause - oracle

Question

I perform daily extractions from the same table. The only thing that ever changes is the range of a column called SAMPLE_ID, so I would like to assign a fixed value to two variables: id_min and id_max so that I can update their values before running the query.
I tried the following:
DECLARE
id_min CONSTANT INTEGER := 17778;
id_max CONSTANT INTEGER := 17803;
BEGIN
SELECT
*
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN id_min AND id_max;
END;
I expected this code to use the numbers assigned to id_min and id_max as the lower and upper bounds of the BETWEEN function in the WHERE clause, but I'm getting this message:
ORA-06550: line 6, column 5:
PLS-00428: an INTO clause is expected in this SELECT statement
It seems someone ran into something similar in this thread, but I do not understand the solutions provided.

Answer 1

Since you are running a PL/SQL code, you cannot just run a SELECT query without doing something with it.
There are some ways on dealing with select queries in PL/SQL.
1) INTO clause, where you take the row returned from the query and assign them to variables. *Notice is said row, not rows. If your query returns more then one row you cannot use INTO clause since it will generate TO_MANY_ROWS exception.
DECLARE
id_min CONSTANT INTEGER := 17778;
id_max CONSTANT INTEGER := 17803;
variable1 your_variable_type;
variable2 your_variable_type;
variable3 your_variable_type;
BEGIN
SELECT
*
INTO
variable1,
variable2,
variable3
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN id_min AND id_max;
---- DO SOMETHING WITH YOUR VARIABLES ----
END;
2) FOR loop if you have one or many rows.
DECLARE
id_min CONSTANT INTEGER := 17778;
id_max CONSTANT INTEGER := 17803;
BEGIN
FOR c IN (
SELECT
*
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN id_min AND id_max
) LOOP
---- DO SOMETHING WITH YOUR VARIABLES ----
---- ACCESS A COLUMN ----
c.column_name;
END LOOP;
END;
3) CURSOR declaring.
DECLARE
id_min CONSTANT INTEGER := 17778;
id_max CONSTANT INTEGER := 17803;
v_cursor SYS_REFCURSOR;
your_variables
...
BEGIN
OPEN v_cursor FOR
SELECT
*
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN id_min AND id_max;
LOOP
FETCH v_cursor INTO your_variables;
EXIT WHEN v_cursor%NOTFOUND;
---- DO SOMETHING WITH YOUR VARIABLES ----
END LOOP;
END;

Answer 2

Once you are between BEGIN and END you are no longer in SQL, but in PLSQL.
In PL/SQL there is no just select statement, there is a "select ... INTO ..." statement instead.
In other words, the database wants from you a variable to save the results to.
Or you might use a loop in order to operate with data.
Below is the loop example to print the data from some_column out
DECLARE
id_min CONSTANT INTEGER := 17778;
id_max CONSTANT INTEGER := 17803;
BEGIN
for score in (SELECT *
FROM MDB.SCORES
WHERE SAMPLE_ID BETWEEN id_min AND id_max) loop
dbms_output.put_line(sc.some_column_name);
end loop;
END;

Answer 3

You might find it simpler to use bind variables, and not run your query in PL/SQL at all.
var id_min NUMBER
var id_max NUMBER
begin
:id_min := 17778;
:id_max := 17803;
end;
/
SELECT
*
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN :id_min AND :id_max;

Answer 4

I did not realize DECLARE would require PL/SQL. I found it easier to do the following using DEFINE.
DEFINE id_min = 17778
DEFINE id_max = 17803;
SELECT
*
FROM
MDB.SCORES
WHERE
SAMPLE_ID BETWEEN &id_min AND &id_max;