What does the keyword "value" mean in this statement, and where would I go to learn more?
What happens if I leave out the keyword "value"? In the code below, z is an entity framework class.
string queryString = "SELECT VALUE q from x.zs as q where q.a = #parm;"
ObjectQuery<z> query = context.CreateQuery<z>
(queryString, new ObjectParameter("parmname",parmvalue));
return query.First();
(This is a part of a practice question for an exam).
The above code is in a function that returns a variable of type z.
That is Entity SQL syntax. Value keyword allows only one value to be specified, and does not add a row wrapper.
Read article about SELECT statement in ESQL
Entity SQL supports two variants of the SELECT clause. The first
variant, row select, is identified by the SELECT keyword, and can be
used to specify one or more values that should be projected out.
Because a row wrapper is implicitly added around the values returned,
the result of the query expression is always a multiset of rows.
Each query expression in a row select must specify an alias. If no
alias is specified,Entity SQL attempts to generate an alias by using
the alias generation rules.
The other variant of the SELECT clause, value select, is identified by
the SELECT VALUE keyword. It allows only one value to be specified,
and does not add a row wrapper.
So, if you want to materialize z object from your query, you should use SELECT VALUE syntax (otherwise you will get exception: cast from MaterializedDataRecord to z type is not valid).
Without VALUE keyword you will get set of rows:
string esql = "SELECT q from x.zs as q where q.a = #parm;";
ObjectQuery<DbDataRecord> query = context
.CreateQuery<DbDataRecord>(esql, new ObjectParameter("parm",parmvalue));
var result = query.First();
Related
I've gone down a bit of a path and hit a wall with how this could be possibly achieved.
Basically, a query is constructed using JPA and passed to an Oracle DB. On the DB there is a Package, used to generate a reference, and this is dynamically named, based on the environment. This value is user-editable, and stored as a DB property within the application. I don't have any control over the architecture of this.
At a pre-JPA stage, a Query String is generated using the reference value for the Package, which is set as a property (again, I can't change the way this has been designed). I set this up using the Query method setParameter(), like so:
(pseudocode replacing the irrelevant parts for focused context)
String referenceRef = [ reference is fetched from DB properties ];
String queryString = "SELECT ?1 FROM sys.dual";
final Query myQuery = getEntityManager().createNativeQuery( queryString );
myQuery.setParameter( 1, referenceRef );
return myQuery.getSingleResult();
I pretty much did this as a reflex, only to realise (in retrospec, quite obviously) that this won't actually work, as it is escaping the element that should not be escaped...
So, where the referenceRef = "DynamicallyNamedPackage.DoThisDynamicallyNamedThing", the above code will just return "DynamicallyNamedPackage.DoThisDynamicallyNamedThing", as it is obviously making it safe, and the point of doing so is, to a certain extent, the antethesis of what I'm trying to do.
Is it possible to achieve this without creating a whole chunk of additional code? All I can currently think of, as an alternative, is to query dba_procedures for all package objects that match, and using the result of that query to construct the queryString (hence circumnavigating using any user-editable values), but it feels like it's going to be convoluted. This is the alternative, which I am using in lieu of an improvement:
final String verifyReference = "SELECT object_name FROM "
+ "dba_procedures WHERE object_type = 'PACKAGE' AND object_name =?1";
final Query refQuery = getEntityManager().createNativeQuery( verifyReference );
refQuery.setParameter( 1, referenceRef );
final String result = refQuery.getSingleResult();
final String queryString = "SELECT " + result + " FROM sys.dual";
final Query myQuery = getEntityManager().createNativeQuery( queryString );
return myQuery.getSingleResult();
It will essentially look up the user-editable property reference against a list of existing packages, then use the result of that query for building the original reference. It has more null checking and so on involved, and does remove the vulnerability, but feels a bit 'unpolished'.
(As has already been mentioned in the comments, this sort of is designed to need a SQL injection, but needs to prevent "SQL Injection" as a definition of not allowing the DB to be manipulated outside of the design by using an unintended value.)
The Oracle dictionary view all_procedures contains a list of all procedures accessible to the current user.
Specifically in the view there are columns OWNER, OBJECT_NAME (=package name), PROCEDURE_NAME.
You may use this view to sanitize the configured input by simple adding an EXISTS subquery such as:
select
?
from dual where exists (
select null from all_procedures
where
OWNER||'.'||OBJECT_NAME||'.'||PROCEDURE_NAME = upper(?) and
object_type = 'PACKAGE');
You will have to bind twice the same input parameter.
The query returns no data if there is not procedure with the given name, so you may raise an exception.
The query above expects a full qualified stored procedure name, i.e. owner.package.procedure, you'll have to adapt it slightly if you allow unqualified names (without the owner).
I have a model Form for table forms. There is a column called guid which can be null, or contain some sort of grouping random hash.
I need to select all forms that have column guid either null or unique in current search. In other words, for repeating guid values in current search I select only first occurence of every guid hash.
I tried:
$results = App\Form::where(... some where clauses .. ).groupBy('guid')
and it's almost ok, but for all rows, where guid == NULL it groups them and selects only one (and I need all of them).
How can I get the unique or null rows either by building proper SQL query or filtering the results in PHP?
Note: I need my $results to be an Illuminate\Database\Eloquent\Builder instance
EDIT:
I fount out that SQL version of query I need is:
SELECT * FROM `forms` WHERE .... GROUP BY IFNULL(guid, id)
What would be equivallent query for Laravel's database query builder?
UPDATE: Using DB::raw
App\Form::where(... conditions ...)
->groupBy(DB::raw("IFNULL('guid', 'id')"));
Or the another way could be:
You can also use whereNotNull, whereNull & at last merge both the collections using merge() like this:
First get the results where guid is grouped by (excluding null guid's here):
$unique_guid_without_null = App\Form::whereNotNull('guid')->groupBy('guid')->get();
Now, get the results where guid is null:
$all_guid_with_null = App\Form::whereNull('guid')->get();
and at last merge both the collections using merge() method:
$filtered_collection = $unique_guid_without_null->merge($all_guid_with_null);
Hope this helps!
For your edited question, you can use raw() as;
->groupBy(DB::raw("IFNULL('guid', 'id')"))
So your final query will be as:
$results = App\Form::where(... some where clauses .. )
->groupBy(DB::raw("IFNULL('guid', 'id')"));
By above query, your $results will be an instance of Illuminate\Database\Eloquent\Builder.
Hello I am trying to put a query member as an filter condition and the code I am trying to do is :
Member [ThisMonth] as VBAMDX.Format(VBAMDX.Now(),"yyyyMM")
SET [currentdays] AS filter([D Date].[DAY ID].Members,
[D Date].[MONTH ID]=[ThisMonth])
But The query did not recognize the Condition
Member [ThisMonth] as VBAMDX.Format(VBAMDX.Now(),"yyyyMM")
SET [currentdays] AS filter([D Date].[DAY ID].Members,
[D Date].[MONTH ID].&[201309])
The query therefore then return the desire result. I am just wondering is there anymore dynamic way to do this?
Thank you very much!
VBAMDX.Format(VBAMDX.Now(),"yyyyMM") returns a string, not a member identifier. This is like in SQL select 'myColumn' from myTable which returns the literal string ´myColumn´ and not the contents of column mycolumn.
If you want to use the Format function, then you firstly need to construct the full unique name of the member, and secondly convert the string to a member identifier using StrToMember:
Member [ThisMonth] as '[D Date].[MONTH ID].&['
+ VBAMDX.Format(VBAMDX.Now(),"yyyyMM")
+ ']' -- this returns a string!
SET [currentdays] AS filter([D Date].[DAY ID].Members,
StrToMember([ThisMonth]))
By the way: You do not need Filter here, and it can slow down queries dramatically, you can just use
SET [currentdays] AS { StrToMember([ThisMonth]) }
I have a complex dynamic query in Eclipselink with a case expression that involves two different columns, one of VARCHAR2 and one of NVARCHAR2.
It needs to be a case expression, because I also want to be able to sort by that result column, so I can't just query both. In Java, both are just mapped as a String, so you don't even see there's a difference.
For my query, Eclipselink creates the following select expression:
CASE
WHEN (t9.STRINGVALUE IS NOT NULL)
THEN t9.STRINGVALUE
ELSE t10.OTHERSTRINGVALUE
END ,
The criteria code is:
Expression<String> str = firstRoot.get("stringValue");
Expression<String> strExp = cb.<String> selectCase().when(cb.isNotNull(str), str)
.otherwise(otherRoot.<String> get("otherStringValue"));
q.multiselect(..., strExp, ...);
which causes Oracle to fail with ORA-12704: character set mismatch. I'd like to modify the code to result in
cast(t10.OTHERSTRINGVALUE as NVARCHAR2(50),
but I cannot find out how.
I tried a converter on the Entity's field, or a .as(String.class) on the .get()-expressions for both fields.
So the question: is there a way to pass an Oracle type like NVARCHAR2 to the .as() expression? Can I otherwise insert a call to CAST(... as NVARCHAR2) with criteria API? Is there any other way to have it generate custom SQL, because I REALLY cannot rewrite the whole query, just because JPA or EL don't provide for the possibility that you might need some custom SQL...
The only way to do it in criteria API is to create a new PathImpl from the otherRoot. get("otherStringValue") path, passing in an EclipseLink native cast expression as the expression node. something like:
PathImpl path = (PathImpl)otherRoot.<String> get("otherStringValue");
Path castPath = new PathImpl(path, em.getMetamodel(), path.getJavaType(), path.getCurrentNode().cast("NVARCHAR2"), path.getModel());
Expression<String> str = firstRoot.get("stringValue");
Expression<String> strExp = cb.<String> selectCase().when(cb.isNotNull(str), str)
.otherwise(castPath );
q.multiselect(..., strExp, ...);
I am using a NamedParameterJdbcTemplate, but found that this problem is in the underlying JdbcTemplate class, so I will show the problem as it occurs with the JdbcTemplate (so let's not worry about the safety of the SQL query here).
Here's what I am trying to achieve:
String sql = "SELECT * FROM clients ORDER BY ? ?";
return jdbcTemplate.query(sql,
new Object[] { "name", "ASC" },
new ClientResultSetExtractor());
I expected the first place-holder to be replaced with "name" and the second with "ASC", which would create the valid SQL query:
SELECT * FROM clients ORDER BY name ASC
But unfortunately, running that jdbc query does not work:
ERROR: syntax error at or near "$2" at character 35
STATEMENT: SELECT * FROM clients ORDER BY $1 $2
What am I doing wrong?
EDIT
I had assumed the problem was the two placeholders in sequence, but even when I remove the first one, it still won't accept just the last one, which should tell the query whether to sort in ASC or DESC order. Is this a bug, and if not, why the heck is this not acceptable????
You're trying to use parameters incorrectly.
Parameters are not column names or SQL statement keywords. They're data content (eg., WHERE LastName = ? is a valid parameterized statement, WHERE ? = 'Smith' is not).