I have following statement in one of the oracle SP:
OPEN CUR_NUM FOR
SELECT RTRIM(LTRIM(num)) as num
FROM USER WHERE USER_ID = v_user_id;
When the above does not return anything the SP result just has no column name in it. But I'd like the cursor to still have num column with some default value like NOTHING when no data is found.
Is this doable ?
If you really need to do that, you could use a UNION to select your dummy-row in case the user_id does not exist:
OPEN CUR_NUM FOR
SELECT RTRIM(LTRIM(num)) AS num
FROM user WHERE USER_ID = v_user_id
UNION ALL
SELECT 'NOTHING' AS num
FROM dual
WHERE NOT EXISTS (
SELECT 1
FROM user
WHERE user_id = v_user_Id
)
two choices i think:
add NVL() around the value if there is a row being returned but the column is null,
otherwise
add a MIN or MAX function if possible - this can force a row to be returned
If this code block is being used in a function, the following would work like a charm:
First, define your return variable
v_ret VARCHAR2(24);
Now, define cursor CUR_NUM as your select statement
CURSOR CUR_NUM IS
SELECT RTRIM(LTRIM(num)) as num
FROM USER WHERE USER_ID = v_user_id;
BEGIN
OPEN CUR_NUM;
FETCH CUR_NUM into v_ret;
CLOSE CUR_NUM;
RETURN nvl(v_ret,'NOTHING');
end;
Related
I'm writing a pl/sql function. I need to select multiple rows from select statement:
SELECT pel.ceid
FROM pa_exception_list pel
WHERE trunc(pel.creation_date) >= trunc(SYSDATE-7)
if i use:
SELECT pel.ceid
INTO v_ceid
it only stores one value, but i need to store all values that this select returns. Given that this is a function i can't just use simple select because i get error, "INTO - is expected."
You can use a record type to do that. The below example should work for you
DECLARE
TYPE v_array_type IS VARRAY (10) OF NUMBER;
var v_array_type;
BEGIN
SELECT x
BULK COLLECT INTO
var
FROM (
SELECT 1 x
FROM dual
UNION
SELECT 2 x
FROM dual
UNION
SELECT 3 x
FROM dual
);
FOR I IN 1..3 LOOP
dbms_output.put_line(var(I));
END LOOP;
END;
So in your case, it would be something like
select pel.ceid
BULK COLLECT INTO <variable which you create>
from pa_exception_list
where trunc(pel.creation_Date) >= trunc(sysdate-7);
If you really need to store multiple rows, check BULK COLLECT INTO statement and examples. But maybe FOR cursor LOOP and row-by-row processing would be better decision.
You may store all in a rowtype parameter and show whichever column you want to show( assuming ceid is your primary key column, col1 & 2 are some other columns of your table ) :
SQL> set serveroutput on;
SQL> declare
l_exp pa_exception_list%rowtype;
begin
for c in ( select *
from pa_exception_list pel
where trunc(pel.creation_date) >= trunc(SYSDATE-7)
) -- to select multiple rows
loop
select *
into l_exp
from pa_exception_list
where ceid = c.ceid; -- to render only one row( ceid is primary key )
dbms_output.put_line(l_exp.ceid||' - '||l_exp.col1||' - '||l_exp.col2); -- to show the results
end loop;
end;
/
SET SERVEROUTPUT ON
BEGIN
FOR rec IN (
--an implicit cursor is created here
SELECT pel.ceid AS ceid
FROM pa_exception_list pel
WHERE trunc(pel.creation_date) >= trunc(SYSDATE-7)
)
LOOP
dbms_output.put_line(rec.ceid);
END LOOP;
END;
/
Notes from here:
In this case, the cursor FOR LOOP declares, opens, fetches from, and
closes an implicit cursor. However, the implicit cursor is internal;
therefore, you cannot reference it.
Note that Oracle Database automatically optimizes a cursor FOR LOOP to
work similarly to a BULK COLLECT query. Although your code looks as if
it fetched one row at a time, Oracle Database fetches multiple rows at
a time and allows you to process each row individually.
I have a table with columns
BIN_1_1
BIN_1_2
BIN_1_3
all the way to BIN_10_10
The user enter a value, and the value needs to be checked in all the columns starting from BIN_1_1 to BIN_10_10.
If there is a duplicate value, it prints a msg and gets out of the procedure / function.
How do I go about this?
Do you mean something like this?
create or replace
procedure check_duplicate( p_val yourtable.bin_1_1%type) is
v_dupl number;
begin
begin
select 1 into v_dupl from yourtable
where p_val in (bin_1_1, bin_1_2, ... bin_10_10) and rownum <=1;
exception
when no_data_found
then v_dupl := 0;
end;
if v_dupl = 1
then
dbms_output.put_line('your message about duplication');
return;
else
dbms_output.put_line('here you can do anything');
end if;
end;
Try this query,
INSERT INTO yourTable values ('your values') where
WHERE BIN_1_1 NOT IN (
SELECT bins FROM (
SELECT BIN_1_1 FROM yourTable
UNION
SELECT BIN_1_2 FROM yourTable
UNION
SELECT BIN_1_3 FROM yourTable
) AS bins
)
P.S. I din't run this query.
Unpivot your table, then it's easy. You may want to write a query that will write the query below for you. ("Dynamic" SQL just to save yourself some work.)
select case when count(*) > 1 then 'Duplicate Found' end as result
from ( select *
from your_table
unpivot (val for col in (BIN_1_1, BIN_1_2, ........, BIN_10_10))
)
where val = :user_input;
Here :user_input is a bind variable - use whatever mechanism works for you (end-user interface, SQL Developer, whatever).
You need to decide what outcome you want when the value is not duplicated in the table - you didn't mention anything about that.
CREATE OR REPLACE PROCEDURE test_max_rows (
max_rows IN NUMBER DEFAULT 1000
)
IS
CURSOR cur_test ( max_rows IN number ) IS
SELECT id FROM test_table
WHERE user_id = 'ABC'
AND ROWNUM <= max_rows;
id test_table.id%TYPE;
BEGIN
OPEN cur_test(max_rows) ;
LOOP
FETCH cur_test INTO id;
EXIT WHEN cur_test%NOTFOUND;
DBMS_OUTPUT.PUT_LINE('ID:' || id);
END LOOP;
END;
My requirement is to modify the above code so that when I pass -1 for max_rows, the proc should return all the rows returned by the query. Otherwise, it should limit the rows as per max_rows.
For example:
EXECUTE test_max_rows(-1);
This command should return all the rows returned by the SELECT statement above.
EXECUTE test_max_rows(10);
This command should return only 10 rows.
You can do this with a OR clause; change:
AND ROWNUM <= max_rows;
to:
AND (max_rows < 1 OR ROWNUM <= max_rows);
Then passing zero, -1, or any negative number will fetch all rows, and any positive number will return a restricted list. You could also replace the default 1000 clause with default null, and then test for null instead, which might be a bit more obvious:
AND (max_rows is null OR ROWNUM <= max_rows);
Note that which rows you get with a passed value will be indeterminate because you don't have an order by clause at the moment.
Doing this in a procedure also seems a bit odd, and you're assuming whoever calls it will be able to see the output - i.e. will have done set serveroutput on or the equivalent for their client - which is not a very safe assumption. An alternative, if you can't specify the row limit in a simple query, might be to use a pipelined function instead - you could at least then call that from plain SQL.
CREATE OR REPLACE FUNCTION test_max_rows (max_rows IN NUMBER DEFAULT NULL)
RETURN sys.odcinumberlist PIPELINED
AS
BEGIN
FOR r IN (
SELECT id FROM test_table
WHERE user_id = 'ABC'
AND (max_rows IS NULL OR ROWNUM <= max_rows)
) LOOP
PIPE ROW (r.id);
END LOOP;
END;
/
And then call it as:
SELECT * FROM TABLE(test_max_rows);
or
SELECT * FROM TABLE(test_max_rows(10));
Here's a quick SQL Fiddle demo. But you should still consider if you can do the whole thing in plain SQL and PL/SQL altogether.
Let's say I have a function call on a select or where clause in Oracle like this:
select a, b, c, dbms_crypto.hash(utl_raw.cast_to_raw('HELLO'),3)
from my_table
A similar example can be constructed for MS SQLServer.
What's the expected behavior in each case?
Is the HASH function going to be called once for each row in the table, or DBMS will be smart enough to call the function just once, since it's a function with constant parameters and no side-effects?
Thanks a lot.
The answer for Oracle is it depends. The function will be called for every row selected UNLESS the Function is marked 'Deterministic' in which case it will only be called once.
CREATE OR REPLACE PACKAGE TestCallCount AS
FUNCTION StringLen(SrcStr VARCHAR) RETURN INTEGER;
FUNCTION StringLen2(SrcStr VARCHAR) RETURN INTEGER DETERMINISTIC;
FUNCTION GetCallCount RETURN INTEGER;
FUNCTION GetCallCount2 RETURN INTEGER;
END TestCallCount;
CREATE OR REPLACE PACKAGE BODY TestCallCount AS
TotalFunctionCalls INTEGER := 0;
TotalFunctionCalls2 INTEGER := 0;
FUNCTION StringLen(SrcStr VARCHAR) RETURN INTEGER AS
BEGIN
TotalFunctionCalls := TotalFunctionCalls + 1;
RETURN Length(SrcStr);
END;
FUNCTION GetCallCount RETURN INTEGER AS
BEGIN
RETURN TotalFunctionCalls;
END;
FUNCTION StringLen2(SrcStr VARCHAR) RETURN INTEGER DETERMINISTIC AS
BEGIN
TotalFunctionCalls2 := TotalFunctionCalls2 + 1;
RETURN Length(SrcStr);
END;
FUNCTION GetCallCount2 RETURN INTEGER AS
BEGIN
RETURN TotalFunctionCalls2;
END;
END TestCallCount;
SELECT a,TestCallCount.StringLen('foo') FROM(
SELECT 0 as a FROM dual
UNION
SELECT 1 as a FROM dual
UNION
SELECT 2 as a FROM dual
);
SELECT TestCallCount.GetCallCount() AS TotalFunctionCalls FROM dual;
Output:
A TESTCALLCOUNT.STRINGLEN('FOO')
---------------------- ------------------------------
0 3
1 3
2 3
3 rows selected
TOTALFUNCTIONCALLS
----------------------
3
1 rows selected
So the StringLen() function was called three times in the first case. Now when executing with StringLen2() which is denoted deterministic:
SELECT a,TestCallCount.StringLen2('foo') from(
select 0 as a from dual
union
select 1 as a from dual
union
select 2 as a from dual
);
SELECT TestCallCount.GetCallCount2() AS TotalFunctionCalls FROM dual;
Results:
A TESTCALLCOUNT.STRINGLEN2('FOO')
---------------------- -------------------------------
0 3
1 3
2 3
3 rows selected
TOTALFUNCTIONCALLS
----------------------
1
1 rows selected
So the StringLen2() function was only called once since it was marked deterministic.
For a function not marked deterministic, you can get around this by modifying your query as such:
select a, b, c, hashed
from my_table
cross join (
select dbms_crypto.hash(utl_raw.cast_to_raw('HELLO'),3) as hashed from dual
);
For SQL server, it will be evaluated for every single row.
You will be MUCH better off by running the function once and assigning to a variable and using the variable in the query.
short answer....it depends.
If the function is accessing data ORACLE does not know if it is going to be the same for each row, therefore, it needs to query for each. If, for example, your function is just a formatter that always returns the same value then you can turn on caching (marking it as Deterministic) which may allow for you to only do the function call once.
Something you may want to look into is ORACLE WITH subquery:
The WITH query_name clause lets you
assign a name to a subquery block. You
can then reference the subquery block
multiple places in the query by
specifying the query name. Oracle
optimizes the query by treating the
query name as either an inline view or
as a temporary table
I got the quoted text from here, which has plenty of examples.
I have a table with a foreign key and a boolean value (and a bunch of other columns that aren't relevant here), as such:
CREATE TABLE myTable
(
someKey integer,
someBool boolean
);
insert into myTable values (1, 't'),(1, 't'),(2, 'f'),(2, 't');
Each someKey could have 0 or more entries. For any given someKey, I need to know if a) all the entries are true, or b) any of the entries are false (basically an AND).
I've come up with the following function:
CREATE FUNCTION do_and(int4) RETURNS boolean AS
$func$
declare
rec record;
retVal boolean = 't'; -- necessary, or true is returned as null (it's weird)
begin
if not exists (select someKey from myTable where someKey = $1) then
return null; -- and because we had to initialise retVal, if no rows are found true would be returned
end if;
for rec in select someBool from myTable where someKey = $1 loop
retVal := rec.someBool AND retVal;
end loop;
return retVal;
end;
$func$ LANGUAGE 'plpgsql' VOLATILE;
... which gives the correct results:
select do_and(1) => t
select do_and(2) => f
select do_and(3) => null
I'm wondering if there's a nicer way to do this. It doesn't look too bad in this simple scenario, but once you include all the supporting code it gets lengthier than I'd like. I had a look at casting the someBool column to an array and using the ALL construct, but I couldn't get it working... any ideas?
No need to redefine functions PostgreSQL already provides: bool_and() will do the job:
select bool_and(someBool)
from myTable
where someKey = $1
group by someKey;
(Sorry, can't test it now)
Similar to the previous one, but in one query, this will do the trick, however, it is not clean nor easily-understandable code:
SELECT someKey,
CASE WHEN sum(CASE WHEN someBool THEN 1 ELSE 0 END) = count(*)
THEN true
ELSE false END as boolResult
FROM table
GROUP BY someKey
This will get all the responses at once, if you only want one key just add a WHERE clause
I just installed PostgreSQL for the first time this week, so you'll need to clean up the syntax, but the general idea here should work:
return_value = NULL
IF EXISTS
(
SELECT
*
FROM
My_Table
WHERE
some_key = $1
)
BEGIN
IF EXISTS
(
SELECT
*
FROM
My_Table
WHERE
some_key = $1 AND
some_bool = 'f'
)
SELECT return_value = 'f'
ELSE
SELECT return_value = 't'
END
The idea is that you only need to look at one row to see if any exist and if at least one row exists you then only need to look until you find a false value to determine that the final value is false (or you get to the end and it's true). Assuming that you have an index on some_key, performance should be good I would think.
(Very minor side-point: I think your function should be declared STABLE rather than VOLATILE, since it just uses data from the database to determine its result.)
As someone mentioned, you can stop scanning as soon as you encounter a "false" value. If that's a common case, you can use a cursor to actually provoke a "fast finish":
CREATE FUNCTION do_and(key int) RETURNS boolean
STABLE LANGUAGE 'plpgsql' AS $$
DECLARE
v_selector CURSOR(cv_key int) FOR
SELECT someBool FROM myTable WHERE someKey = cv_key;
v_result boolean;
v_next boolean;
BEGIN
OPEN v_selector(key);
LOOP
FETCH v_selector INTO v_next;
IF not FOUND THEN
EXIT;
END IF;
IF v_next = false THEN
v_result := false;
EXIT;
END IF;
v_result := true;
END LOOP;
CLOSE v_selector;
RETURN v_result;
END
$$;
This approach also means that you are only doing a single scan on myTable. Mind you, I suspect you need loads and loads of rows in order for the difference to be appreciable.
You can also use every, which is just an alias to bool_and:
select every(someBool)
from myTable
where someKey = $1
group by someKey;
Using every makes your query more readable. An example, show all persons who just eat apple every day:
select personId
from personDailyDiet
group by personId
having every(fruit = 'apple');
every is semantically the same as bool_and, but it's certainly clear that every is more readable than bool_and:
select personId
from personDailyDiet
group by personId
having bool_and(fruit = 'apple');
Maybe count 'all' items with somekey=somevalue and use it in a boolean comparison with the count of all 'True' occurences for somekey?
Some non-tested pseudo-sql to show what i mean...
select foo1.count_key_items = foo2.count_key_true_items
from
(select count(someBool) as count_all_items from myTable where someKey = '1') as foo1,
(select count(someBool) as count_key_true_items from myTable where someKey = '1' and someBool) as foo2
CREATE FUNCTION do_and(int4)
RETURNS boolean AS
$BODY$
SELECT
MAX(bar)::bool
FROM (
SELECT
someKey,
MIN(someBool::int) AS bar
FROM
myTable
WHERE
someKey=$1
GROUP BY
someKey
UNION
SELECT
$1,
NULL
) AS foo;
$BODY$
LANGUAGE 'sql' STABLE;
In case you don't need the NULL value (when there aren't any rows), simply use the query below:
SELECT
someKey,
MIN(someBool::int)::bool AS bar
FROM
myTable
WHERE
someKey=$1
GROUP BY
someKey
SELECT DISTINCT ON (someKey) someKey, someBool
FROM myTable m
ORDER BY
someKey, someBool NULLS FIRST
This will select the first ordered boolean value for each someKey.
If there is a single FALSE or a NULL, it will be returned first, meaning that the AND failed.
If the first boolean is a TRUE, then all other booleans are also TRUE for this key.
Unlike the aggregate, this will use the index on (someKey, someBool).
To return an OR, just reverse the ordering:
SELECT DISTINCT ON (someKey) someKey, someBool
FROM myTable m
ORDER BY
someKey, someBool DESC NULLS FIRST