Does apex_string.split always guarantee that the order of the rows returned is the order of the characters of the string ?
Can I rely on the rownum to always correspond to 1 for the first character of the split string ?
or do I need to add a order by rownum ?
What is the method to get the rows in the same order of the characters of the string ?
My requirement is to insert the rows returned by apex_string.split in the same order as the characters of the string.
I am currently executing the below, will this maintain the character order ?
select t.column_value value, rownum seq
from table(apex_string.split('test','')) t
bulk collect into ins_arr;
for i in ins_arr.first..ins_arr.last
loop
/* execute insert statement */
insert into table (seq, value )
values (ins_arr.seq,ins_arr.value);
end loop
The insert should result in
seq
value
1
t
2
e
3
s
4
t
Thank you in advance,
I don't think it's guaranteed, becuase if it was, it would be in the documentation. But I think you can accomplish what you want by changing your routine. (Note, I have not verified this.)
insert into table (seq, value)
select t.column_value value,
row_number() over (order by t.column_value)
from table(apex_string.split('test','')) t
I think you can do the same with rownum, but I'm never 100% sure what order the rownum and the order by happen in.
Related
I have a test script that I'm beggining to play with. I'm getting stuck with something that seems simple.
I want to iterate through rows to fetch data from last row of result set to use only it.
procedure e_test_send
is
cursor get_rec is
select
id,
email_from,
email_to,
email_cc,
email_subject,
email_message
from test_email_tab;
begin
for rec_ in get_rec loop
ifsapp.send_email_api.send_html_email(rec_.email_to,rec_.email_from, rec_.email_subject, rec_.email_message);
end loop;
end e_test_send;
All I'm trying to do is send an email with a message and to a person from the last row only. This is a sample table that will grow in records. At the minute I have 2 rows of data in it, if I execute this procedure it will send 2 emails which is not the desired action.
I hope this makes sense.
Thanks
Do you know which row is the last row? The one with the MAX(ID) value? If so, then you could base cursor on a straightforward
SELECT id,
email_from,
email_to,
email_cc,
email_subject,
email_message
FROM test_email_tab
WHERE id = (SELECT MAX (id) FROM test_email_tab)
As it scans the same table twice, its performance will drop as number of rows gets higher and higher. In that case, consider
WITH
temp
AS
(SELECT id,
email_from,
email_to,
email_cc,
email_subject,
email_message,
ROW_NUMBER () OVER (ORDER BY id DESC) rn
FROM test_email_tab)
SELECT t.id,
t.email_from,
t.email_to,
t.email_cc,
t.email_subject,
t.email_message
FROM temp t
WHERE t.rn = 1
which does it only once; sorts rows by ID in descending order and returns the one that ranks as the "highest" (i.e. the last).
I have question about "Subquery in Order by clause". The below request returns the error. Is it means that Subquery in Order by clause must be scalar?
select *
from employees
order by (select * from employees where first_name ='Steven' and last_name='King');
Error:
ORA-00913: too many values
00913. 00000 - "too many values"
Yes, it means that if you use a subquery in ORDER BY it must be scalar.
With select * your subquery returns multiple columns and the DBMS would not know which of these to use for the sorting. And if you selected one column only, you would still have to make sure you only select one row of course. (The difference is that Oracle sees the too-many-columns problem immediately, but detect too many rows only when fetching the data.)
This would be allowed:
select * from employees
order by (select birthdate from employees where employee_id = 12345);
This is a scalar query, because it returns only one value (one column, one row). But of course this still makes as little sense as your original query, because the subquery result is independent from the main query, i.e. it returns the same value for every row in the table and thus no sorting takes effect.
A last remark: A subquery in ORDER BY makes very seldomly sense, because that would mean you order by something you don't display. The exception is when looking up a sortkey. E.g.:
select *
from products p
where type = 'shirt' and color = 'blue' and size in ('S', 'M', 'L', 'XL')
order by (select sortkey from sizes s where s.size = p.size);
It means that valid options for ORDER BY clause can be
expression,
position or
column alias
A subquery is neither of these.
Am trying to list top 3 records from atable based on some amount stored in a column FTE_TMUSD which is of varchar datatype
below is the query i tried
SELECT *FROM
(
SELECT * FROM FSE_TM_ENTRY
ORDER BY FTE_TMUSD desc
)
WHERE rownum <= 3
ORDER BY FTE_TMUSD DESC ;
o/p i got
972,9680,963 -->FTE_TMUSD values which are not displayed in desc
I am expecting an o/p which will display the top 3 records of values
That should work; inline view is ordered by FTE_TMUSD in descending order, and you're selecting values from it.
What looks suspicious are values you specified as the result. It appears that FTE_TMUSD's datatype is VARCHAR2 (ah, yes - it is, you said so). It means that values are sorted as strings, not numbers - and it seems that you expect numbers. So, apply TO_NUMBER to that column. Note that it'll fail if column contains anything but numbers (for example, if there's a value 972C).
Also, an alternative to your query might be use of analytic functions, such as row_number:
with temp as
(select f.*,
row_number() over (order by to_number(f.fte_tmusd) desc) rn
from fse_tm_entry f
)
select *
from temp
where rn <= 3;
I need help
i have records 123,456,789 in rows when i am execute like
this one is working
select * from table1 where num1 in('123','456')
but when i am execute
select * from table1 where num1 in(select value from table2)
no resultset found - why?
Check the DataType varchare2 or Number
try
select * from table1 where num1 in(select to_char(value) from table2)
Storing comma separated values could be the cause of problem.
You can try using regexp_substr to split comma.
First and foremost, an important thing to remember: Do not store numbers in character datatypes. Use NUMBER or INTEGER. Secondly, always prefer VARCHAR2 datatype over CHAR if you wish to store characters > 1.
You said in one of your comments that num1 column is of type char(4). The problem with CHAR datatype is that If your string is 3 characters wide, it stores the record by adding extra 1 space character to make it 4 characters. VARCHAR2 only stores as many characters as you pass while inserting/updating and are not blank padded.
To verify that you may run select length(any_char_col) from t;
Coming to your problem, the IN condition is never satisfied because what's actually being compared is
WHERE 'abc ' = 'abc' - Note the extra space in left side operator.
To fix this, one good option is to pad the right side expression with as many spaces as required to do the right comparison.The function RPAD( string1, padded_length [, pad_string] ) could be used for this purpose.So, your query should look something like this.
select * from table1 where num1 IN (select rpad(value,4) from table2);
This will likely utilise an index on the column num1 if it exists.
The other one is to use RTRIM on LHS, which is only useful if there's a function based index on RTRIM(num1)
select * from table1 where RTRIM(num1) in(select value from table2);
So, the takeaway from all these examples is always use NUMBER types to store numbers and prefer VARCHAR2 over CHAR for strings.
See Demo to fully understand what's happening.
EDIT : It seems You are storing comma separated numbers.You could do something like this.
SELECT *
FROM table1 t1
WHERE EXISTS (
SELECT 1
FROM table2 t2
WHERE ',' ||t2.value|| ',' LIKE '%,' || rtrim(t1.num1) || ',%'
);
See Demo2
Storing comma separated values are bound to cause problems, better change it.
Let me tell you first,
You have stored values in table2 which is comma seperated.
So, how could you match your data with table1 and table2.
Its not Possible.
That's why you did not get any values in result set.
I found the Solution using string array
SELECT T.* FROM TABLE1 T,
(SELECT TRIM(VALUE)AS VAL FROM TABLE2)TABLE2
WHERE
TRIM(NUM1) IN (SELECT COLUMN_VALUE FROM TABLE(FUNC_GETSTRING_ARRAY(TABLE2.VAL)))
thanks
I have a table with 3 columns:
table1: ID, CODE, RESULT, RESULT2, RESULT3
I have this SAS code:
data table1
set table1;
BY ID, CODE;
IF FIRST.CODE and RESULT='A' THEN OUTPUT;
ELSE IF LAST.CODE and RESULT NE 'A' THEN OUTPUT;
RUN;
So we are grouping the data by ID and CODE, and then writing to the dataset if certain conditions are met. I want to write a hive query to replicate this. This is what I have:
proc sql;
create table temp as
select *, row_number() over (partition by ID, CODE) as rowNum
from table1;
create table temp2 as
select a.ID, a.CODE, a.RESULT, a.RESULT2, a.RESULT3
from temp a
inner join (select ID, CODE, max(rowNum) as maxRowNum
from temp
group by ID, CODE) b
on a.ID=b.ID and a.CODE=b.CODE
where (a.rowNum=1 and a.RESULT='A') or (a.rowNum=b.maxRowNum and a.RESULT NE 'A');
quit;
There are two issues I see with this.
1) The row that is first or last in each BY group is entirely dependant on the order of rows in table1 in SAS, we aren't ordering by anything. I don't think row order is preserved when translating to a hive query.
2) The SAS code is taking the first row in each BY GROUP or the last, not both. I think that my HIVE query is taking both, resulting in more rows than I want.
Any suggestions or insight on how to improve my query is appreciated. Is it even possible to replicate this SAS code in HIVE?
The SAS code has a by statement (BY ID CODE;), which tells SAS that the set dataset is sorted at those levels. So, not a random selection for first. and last..
That said, we can replicate this in HIVE by using the first_value and last_value window functions.
FIRST.CODE should replicate to
first_value(code) over (partition by Id order by code)fcode
Similarly, LAST.CODE would be
last_value(code) over (partition by Id order by code)lcode
Once you have the fcode and lcode columns, use case when statements for the result column criteria. Like,
case when (code=fcode and result='A') or (code=lcode and result<>'A')
then 1 else 0 end as op_flag
Then the fetch the table with where op_flag = 1
SAMPLE
select id, code, result from (
select *,
first_value(code) over (partition by id order by code)fcode,
last_value(code) over (partition by id order by code)lcode
from footab) f
where (code=fcode and result='A') or (code=lcode and result<>'A')
Regarding point 1) the BY group processing requires the input data to be sorted or indexed on BY variables, so though the code contains no ordering, the source data is processed in order. If the input data was not indexed/sorted, SAS will throw error.
Regarding this, possible differences are on rows with same values of BY variables, especially if the RESULT is different.
In SAS, I would pre-sort data by ID, CODE, RESULT, then use BY ID CODE in order to not be influenced by order of rows.
Regarding 2) FIRST and LAST can be both true in SAS. Since your condition for first and last on RESULT is different, I guess this is not a source of differences.
I guess you could add another field as
row_number() over (partition by ID, CODE desc) as rowNumDesc
to detect last row with rowNumDesc = 1 (so that you skip the join).
EDIT:
I think the two programs above both include random selection of rows for groups with same values of ID and CODE variables, especially with same values of RESULT. But you should get same number of rows from both. If not, just debug it.
However the random aspect in SAS code/storage is based on physical order of rows, while the ROW_NUMBERs randomness within a group will be influenced by the implementation of the function in the engine.