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How not to consider all of the parameters in the WHERE clause of an IB procedure
Hi,
how can i arrange a WHERE clause in a database select procedure in Interbase, if not all of the values of the input parameters should always be considered ?
Example: i have 3 input parameters: year, account_no and color. Sometimes i want to return only the records which match the given color (the other two parameters aren't important) - so the WHERE part of the sql statement would look like "WHERE table.color = :color"; on the other hand, sometimes i need also to consider the value of the year parameter -> the where part is: "WHERE table.color = :color AND table.year = :year". As you can see i should be able to consider any possible combination of the parameters.
In Delphi i can easily do that, because i build an sql statement dynamically (in a string) and then assign it to a IBQuery. Is it possible to do the same (or similar) thing also in IB ( to dynamically change the content of a WHERE clause ), or is the database procedure somehow "hardcoded" and you can't assign a string to the WHERE clause (the string could also be an input parameter)?
The result i want to achieve is to have only one procedure (or better, only one select clause) for all possible combinations of the input parameters. The example presented here has 3 parameters, but in my application i have 10 of them, so it would be practically impossible to write an select clause for every possible combination of the parameters.
Is it maybe another way to do that?
Thanx
how can i arrange a WHERE clause in a database select procedure in Interbase, if not all of the values of the input parameters should always be considered ?
Example: i have 3 input parameters: year, account_no and color. Sometimes i want to return only the records which match the given color (the other two parameters aren't important) - so the WHERE part of the sql statement would look like "WHERE table.color = :color"; on the other hand, sometimes i need also to consider the value of the year parameter -> the where part is: "WHERE table.color = :color AND table.year = :year". As you can see i should be able to consider any possible combination of the parameters.
In Delphi i can easily do that, because i build an sql statement dynamically (in a string) and then assign it to a IBQuery. Is it possible to do the same (or similar) thing also in IB ( to dynamically change the content of a WHERE clause ), or is the database procedure somehow "hardcoded" and you can't assign a string to the WHERE clause (the string could also be an input parameter)?
The result i want to achieve is to have only one procedure (or better, only one select clause) for all possible combinations of the input parameters. The example presented here has 3 parameters, but in my application i have 10 of them, so it would be practically impossible to write an select clause for every possible combination of the parameters.
Is it maybe another way to do that?
Thanx
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The way that I have handled situations like this is:
SELECT * FROM TABLE_FOO
WHERE (:year IS NULL OR year=:year)
AND (:account_no IS NULL OR account_no=:account_no)
AND (:color IS NULL OR color=:color);
and so on and so forth. If any single parameter is set to NULL it is basically ignored in the select statement. You are still required to have all the parameters as input to the procedure but you can now have control over which of them matter.
Hope it helps.
SELECT * FROM TABLE_FOO
WHERE (:year IS NULL OR year=:year)
AND (:account_no IS NULL OR account_no=:account_no)
AND (:color IS NULL OR color=:color);
and so on and so forth. If any single parameter is set to NULL it is basically ignored in the select statement. You are still required to have all the parameters as input to the procedure but you can now have control over which of them matter.
Hope it helps.
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Janos