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Posted by --CELKO-- on 10/01/24 11:41
Try this as an example, with one of my cut & paste for cutting up a CSV
list
This is a common Newbie question. This shows that you don't know SQL
uses only scalar parameters and has only one data structure, the table.
This is a fundamental programming concept that you should learn in the
first week of any SQL language class. SQL is not your original
procedural programming language.
1) The dangerous, slow kludge is to use dynamic SQL and admit that any
random furure user is a better programmer than you are. It is used by
Newbies who do not understand SQL or even what a compiled language is.
A string is a string; it is a scalar value like any other parameter; it
is not code. Again, this is not just an SQL problem; this is a basic
misunderstanding of programming principles.
2) Passing a list of parmeters to a stored procedure can be done by
putting them into a string with a separator. I like to use the
traditional comma. Let's assume that you have a whole table full of
such parameter lists:
CREATE TABLE InputStrings
(keycol CHAR(10) NOT NULL PRIMARY KEY,
input_string VARCHAR(255) NOT NULL);
INSERT INTO InputStrings VALUES ('first', '12,34,567,896');
INSERT INTO InputStrings VALUES ('second', '312,534,997,896');
etc.
This will be the table that gets the outputs, in the form of the
original key column and one parameter per row.
CREATE TABLE Parmlist
(keycol CHAR(10) NOT NULL,
parm INTEGER NOT NULL);
It makes life easier if the lists in the input strings start and end
with a comma. You will need a table of sequential numbers -- a
standard SQL programming trick, Now, the query, in SQL-92 syntax
(translate into your local dialect):
INSERT INTO ParmList (keycol, parm)
SELECT keycol,
CAST (SUBSTRING (I1.input_string
FROM S1.seq
FOR MIN(S2.seq) - S1.seq -1)
AS INTEGER)
FROM InputStrings AS I1, Sequence AS S1, Sequence AS S2
WHERE SUBSTRING (',' || I1.input_string || ',' FROM S1.seq FOR 1) =
','
AND SUBSTRING (',' || I1.input_string || ',' FROM S2.seq FOR 1) =
','
AND S1.seq < S2.seq
GROUP BY I1.keycol, I1.input_string, S1.seq;
The S1 and S2 copies of Sequence are used to locate bracketing pairs of
commas, and the entire set of substrings located between them is
extracted and cast as integers in one non-procedural step. The trick
is to be sure that the right hand comma of the bracketing pair is the
closest one to the first comma. You can add a computation for the
relative postion of each element in the list (left as a exercise for
the student)
You can then write:a query like this:
SELECT *
FROM Foobar
WHERE x IN (SELECT parm FROM Parmlist WHERE parm IS NOT NULL);
Hey, I can write kludges with the best of them, but I don't. You need
to at the very least write a routine to clean out blanks and
non-numerics in the strings, take care of floating point and decimal
notation, etc. Basically, you must write part of a compiler in SQL.
Yeeeech! Or decide that you do not want to have data integrity, which
is what most Newbies do in practice altho they do not know it.
3) The right way is to use tables with the IN () predicate, You set up
the procedure declaration with a "fake array" made from a repeated
gorup, like this in SQL/PSM (translate into your local dialect):
CREATE PROCEDURE Foobar ( <other parameters>, IN p1 INTEGER, IN p2
INTEGER, .. IN pN INTEGER) -- default missing values to NULLs
BEGIN
SELECT foo, bar, blah, yadda, ...
FROM Floob
WHERE my_col
IN (SELECT DISTINCT parm -- kill redundant dups
FROM (VALUES (p1), (p2), .., (pN)) AS ParmList(parm)
WHERE parm IS NOT NULL -- ignore empty aparameters
AND <other conditions>)
AND <more predicates>;
<more code>;
END;
The idea is that creating a derived table will perform better .You can
also add functions to the parameters like UPPER(pi), apply CASE
expressions like in T-SQL
(CASE WHEN @p1 = 'usa' THEN @p2 ELSE 2.2 * @p2 END)
or use scalar subqueries like this on subsets of the parameters:
(SELECT L.address_code
FROM Locations AS L
WHERE @p1 = L.longitude
AND @p2 = L.latitude
AND @p3 = 'Paris');
SQL Server can have up to 1,024 parameters in a stored procedure and
that is usually good enough. If not, make two calls to the procedure
but have you ever seen a procedure in any language with over 1,024
parameters?
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