mysql large query does not respond

we have table with around 9 hundred thousand records. we are trying to execute a query with having large data (NOTE: the query is large )

like <some query> and agt.item in (',productRange,.......<very large data, having around 2 lakh chars>)

with this the query is failing saying syntax error. but with less number of items in query it executes. Please let me know how to handle this kind of issues.

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Most DBMS works terrible with large parameter lists. So if you have a large "IN" list, e.g.

SELECT *
FROM   foo
WHERE  bar IN ('1','2','3','4'...,'500000')

you will get very poor performance compared with having a table containing all values you want to select on, and joining the two tables:

CREATE TABLE baz (
    bar VARCHAR
)

INSERT INTO baz(bar) VALUES ('1');
INSERT INTO baz(bar) VALUES ('2');
INSERT INTO baz(bar) VALUES ('3');
INSERT INTO baz(bar) VALUES ('4');
...
INSERT INTO baz(bar) VALUES ('500000');

SELECT *
FROM   foo,
       baz
WHERE  foo.bar = baz.bar

So, as MySQL does not have table valued parameters your best bet is to store the data in a temp table instead of typing it out in the query, and don't forget you will need an index on the value you are filtering on (agt.item in your case).