You should always put validation rules in the database (e.g. CHECK
constraints) of course. To use a very simple example:

CREATE TABLE Test (
col1 INTEGER NOT NULL,
col2 INTEGER NOT NULL,
CHECK (col1 < col2)
);

You could write a procedure (parameter query) like this:

CREATE PROCEDURE TestProc1 (
arg_col1 INTEGER,
arg_col2 INTEGER
) AS
INSERT INTO Test (col1, col2)
VALUES (arg_col1, arg_col2);

However, when the parameter values fail the check you get an error e.g.

EXECUTE TestProc1 1, 2;  -- No error, one row affected
EXECUTE TestProc1 99, 3;  -- Error

To answer your question, yes you can use a query to ensure only valid
data is used. To revise the above proc:

CREATE PROCEDURE TestProc2 (
arg_col1 INTEGER,
arg_col2 INTEGER
) AS
INSERT INTO Test (col1, col2)
SELECT DISTINCT arg_col1 AS col1, arg_col2 AS col2
FROM Test AS T1
WHERE arg_col1 < arg_col2;

Invalid (integer) values no long cause an error:

EXECUTE TestProc1 1, 2;  -- No error, one row affected (insert
succeeds)
EXECUTE TestProc1 99, 3;  -- No error, no rows affected (insert fails)

Jamie.

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