Is it possible in a Microsoft Access query to use the Rnd() Function without specifying a numeric column (e.g. when my Primary Key contains Alpha characters) and still generate a different random number for each row?
You could use the 1st character;
rnd(asc(left([field],1)))
which should give a different result for each row, even if the char is the same
It's simpler than I originally thought, this function can be used in exactly the same context as Rnd()
Public Function Rand(FieldName) As Single
Rand = Rnd(1)
End Function
Then in SQL used as:
SELECT ID, Rand([ID]) FROM Table
By passing it a fieldname, we force the function to execute for each row in the query (eventhough we ignore the actual field in the function) and then evaluating the function to 1 will always return a different random number in the same way Rnd() would if executed in VB.
Related
I have an entity. One field named "number" consists of String. It is a number + some text information. For example:
131-MOD
11853-ARO
983-AKK
etc.
My task is: get the maximum of the first number. So, I have to extract Integer value from String "number" and find the maximum from it. For the examples higher, it would be the numbers 131, 11853 and 983. So, the maximum is 11853. I have to get this Integer value as a result.
Here i have my try using Hibernate. But it working with only Integer values. How to extract number, i have no idea.
public Integer getMaxNumber()
{
return (Integer) getSessionFactory().getCurrentSession().createQuery("select max(id) from EmployeeTripCard s").uniqueResult();
}
How can i do that?
You may use the following JPQL query:
SELECT
MAX(CAST(SUBSTRING(id, 1, LOCATE(id, '-') - 1) AS INTEGER))
FROM EmployeeTripCard s;
We can use LOCATE to find the index of the first -, then call SUBSTRING to find the initial number. Note carefully that we also need to cast this resulting string to an integer, in order for MAX to behave the way we want (numbers as text don't always sort the same way as actual pure numbers).
I have three variables that are declared and have an integer value assigned to them.
I am trying to randomly assign the integer value to a field in an UPDATE statement, but get an error.
This is statement I am trying to execute:
FOR user_record IN (SELECT * FROM users_to_add) LOOP
UPDATE
customer."user"
SET
primary_site_id = ({site_GRO, site_WHS, site_SHR}[])[ceil(random()*3)],
WHERE
userid = (SELECT userID FROM customer.user
WHERE emailaddress=user_record.email_address);
END LOOP;
I am getting:
SyntaxError: syntax error at or near "{"
This same format works if the value being randomly selected is a string but since these are variables, the inside curly brackets can't be enclosed in quotes.
Use an ARRAY constructor instead of the (invalid) array literal.
(ARRAY[site_GRO, site_WHS, site_SHR])[ceil(random()*3)]
However, a set-based solution is typically more efficient than looping:
UPDATE customer."user" u
SET primary_site_id = CASE trunc(random()*3)::int
WHEN 0 THEN site_gro -- your variables here
WHEN 1 THEN site_whs
WHEN 2 THEN site_shr
END
FROM users_to_add ua
WHERE u.userid = ua.email_address;
Should achieve the same. Works inside a PL/pgSQL block or as standalone SQL DML command (then you need to interpolate variable values yourself).
A single multi-row UPDATE is much cheaper than many updates in a loop.
trunc() is slightly more correct than ceil(), as random() returns a value in the domain [0,1) (1 excluded). It's also faster.
And a CASE construct is substantially faster than building an array just to extract a single element from it.
Asides:
Avoid reserved words like user as identifiers. Always requires double-quoting, and can lead to confusing errors when forgotten.
Also avoid random capitalization in identifiers. This goes for SQL as well as for PL/pgSQL. See:
Are PostgreSQL column names case-sensitive?
Perhaps you can try splitting the index and array out into their own vars?
FOR user_record IN (SELECT * FROM users_to_add) LOOP
a := ARRAY[site_GRO, site_WHS, site_SHR];
i := ceil(random()*3);
UPDATE
customer."user"
SET
primary_site_id = a[i]
WHERE
userid = (SELECT userID FROM customer.user WHERE emailaddress=user_record.email_address);
END LOOP;
On an Oracle DB I have a table with SDO_GEOMETRY objects. I would like to query the database for those polygons with less than x edges. In theory this would be easy with a query like
SELECT * FROM myTable t WHERE LENGTH(t.geometry.sdo_ordinates) < x
Obviously the LENGTH funtion is defined for char and the type of
t.geometry.sdo_ordinates is oracle.sql.ARRAY so that doesn't work. Shouldn't there be a trivial way to SELECT the length or an array in Oracle? Somehow I'm unable to get the syntax right.
PS: I kind of solved my search with the following query, still the original questerion remains, isn't there an array size/length function?
SELECT * FROM myTable t WHERE LENGTH(t.geomety.Get_WKT()) < (x * c)
No, there is no simple sql function that counts the elements of an array.
However as mentioned here, another idea is a PL/SQL script.
create or replace function get_count(ar in SDO_ORDINATE_ARRAY) return number is
begin
return ar.count;
end get_count;
t.geometry.sdo_ordinates.COUNT is a PL/SQL attribute that can be used within functions/procedures. Thus that is not a function useable in plain SQL.
Attribute:
value.someAttribute
Function:
doSomething(value)
Clarification: Functions have return values, procedures don't. Source
I have a table called documents one of the fields is called location which shows the file path for the document. I need to change it from D:\........ to H:\.....
How can I do this using update in sql as the file paths vary in length and there are lots of records
You can use string helper function to achieve the same. Something like below
UPDATE documents SET location = 'H:' + Mid(location, 2, Len(location) - 2)
WHERE Left(location, 1) = 'D'
Here, Len() function returns the length of the string literal
Left() function returns 1 character from the left of the string literal
Mid() function give you substring from a string (starting at any position)
See MS Access: Functions for more information on the same.
I have a db2 function returning an integer. As per my limited knowledge the only way to see this function working is using to return column in a query like the example below.
Is there a way to display a return value of a function given a parameter withoyt building up a more complex query?
Example
I have a function
myfoo(index integer) returns integer ...
And I am using it in a more complex quewry like
select myIndex, myfoo(myIndex), myValue from MyTable...
If I try to get the following
select from myfoo(3)
it will not work.
Is there any db2 function to print out the return value of that function without error?
SELECT myfoo(3) FROM SYSIBM.SYSDUMMY1
SYSIBM.SYSDUMMY1 is a special "dummy" table that contains a single row, the equivalent of Oracle's DUAL.
If you have the compatibility vector, you can even use Oracle's Dual table. http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.apdv.porting.doc/doc/r0052874.html
Also, you can use the 'values' sentence. For example,
values myfoo(myIndex)