Result of sysdate-timstamp

Question

Hi,
I am trying to get the date and time stamp difference by : SYSDATE- some time stamp;
using the query:
SELECT SYSDATE-(SELECT TXN_TIMESTAMP FROM (SELECT ROWNUM,TXN_TIMESTAMP FROM ACCOUNT_tXN WHERE TXN_aCCOUNT_NO=acct ORDER BY 2 DESC) WHERE ROWNUM=1) INTO days FROM DUAL;
this query working fine and returning the difference between these two on the Sql prompt, but when I am trying to execute it in Pl-Sql then I had to add
one INTO DAYS into it.
what will be the data type of DAYS.
it is returning out put like: +00000001 5:30:23.00 PM so what should be the data type of days.
I tried
1> timestamp;
2>date
3> number
4>interval days to second
but it didn't worked.
please suggest as what should be the data type of DAYS.
Jitendra

Answer 1

please suggest as what should be the data type of DAYS.
The simplest way to know what datatypes Oracle creates for expressions is to use CTAS and create a table from the query.
CREATE TABLE myTable AS SELECT * FROM myRestOfQuery;
Then examine the DDL for the table that Oracle created to see what datatype is used.
The other issue may run into when you used expressions to create result set columns is that Oracle will use the first row returned to determine the datatype. This means that the actual datatype may not have the PRECISION that is needed for data coming later. For example the first row may have a value that is only 5 characters long but later data may be much longer.