In the JDBC code, I have the following that is working with SQL Server:
CallableStatement stmt = connection.prepareCall("{ call getName() }");
ResultSet rs = stmt.executeQuery();
if(rs != null)
{
while(rs.next())
{
//do something with rs.getString("name")
}
}
Multiple rows are returned for the above situation.
I understand that the use of a cursor is required to loop through the table in Oracle, but is there any way to keep the above code the same and accomplish the same thing?
Sample PL/SQL code would be much appreciated.
Thanks in advance.
You could implement getName() as a pipelined function:
CREATE OR REPLACE name_record AS OBJECT ( name VARCHAR2(100) );
/
CREATE OR REPLACE name_table AS TABLE OF name_record;
/
CREATE OR REPLACE FUNCTION getName RETURN name_table PIPELINED
AS
n name_record;
BEGIN
-- I have no idea what you're doing here to generate your list of names, so
-- I'll pretend it's a simple query
FOR i IN (SELECT name FROM someTable) LOOP
n := name_record( i.name );
PIPE ROW(n);
END LOOP;
END;
/
You would need to change the actual query in Java to SELECT name FROM TABLE(getName()).
This is straight JDBC, so it'll work with any database that has a valid JDBC driver.
It assumes, of course, that the stored proc exists in both and that you aren't using any non-standard, vendor-proprietary code in your class.
Related
I ran into another issue with using a data reader around a sproc with multiple ref cursors coming out. I am getting a not supported exception. Unfortunately, i can see from where it is coming from the source code of npgsql however.. i am not sure if i agree with throwing that exception. The code we have written works with oracle (both fully managed and managed flavors), sql server. Any help appreciated to keep it consistent for an api across some of those key flavors of dbms out there.
sproc body
CREATE OR REPLACE FUNCTION public.getmultipleresultsets (
v_organizationid integer)
RETURNS Setof refcursor
LANGUAGE 'plpgsql'
AS $BODY$
declare public override void AddCursorOutParameter(DbCommand command,
string RefCursorName)
{
NpgsqlParameter parameter = (NpgsqlParameter)CreateParameter(RefCursorName, false);
parameter.NpgsqlDbType = NpgsqlDbType.Refcursor;
parameter.NpgsqlValue = DBNull.Value;
parameter.Direction = ParameterDirection.Output;
command.Parameters.Add(parameter);
}
cv_1 refcursor;
cv_2 refcursor;
BEGIN
open cv_1 for
SELECT a.errorCategoryId, a.name, a.bitFlag
FROM ErrorCategories a
ORDER BY name;
RETURN next cv_1;
open cv_2 for
SELECT *
FROM StgNetworkStats ;
RETURN next cv_2;
END;
$BODY$;
Key Reader code that wraps postgres sql (Entlib implementation of npgsql)
private IDataReader DoExecuteReader(DbCommand command, CommandBehavior cmdBehavior)
{
try
{
var sql = new StringBuilder();
using (var reader = command.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (reader.Read())
{
sql.AppendLine($"FETCH ALL IN \"{ reader.GetString(0) }\";");
}
}
command.CommandText = sql.ToString();
command.CommandType = CommandType.Text;
IDataReader reader2 = command.ExecuteReader(cmdBehavior);
return reader2;
}
catch (Exception)
{
throw;
}
}
The command building code is shown below
Helper.InitializeCommand(cmd, 300, "getmultipleresultsets");
db.AddReturnValueParameter(cmd);
db.AddInParameter(cmd, "organizationId", DbType.Int32, ORGANIZATIONID);
db.AddCursorOutParameter(cmd, "CV_1");
db.AddCursorOutParameter(cmd, "CV_2
The code that adds the refcursor parameter goes something like this
You code above seems to garble the PostgreSQL function with the .NET client code attempting to read its result.
Regardless, your function is declared to return a set of refcursors - this is not the same as two output parameters; you seem to be confusing the name of the cursor (cursors have names, but not ints, for example) with the name of the parameter (int parameters do have names).
Please note that PostgreSQL does not actually have output parameters - a function always returns a single table, and that's it. PostgreSQL does have a function syntax with output parameters, but that is only a way to construct the schema of the output table. This is unlike SQL Server, which apparently can return both a table and a set of named output parameters. To facilitate portability, when reading results, if Npgsql sees any NpgsqlParameter with direction out, it will attempt to find a resultset with the name of the parameter and will simply populate the NpgsqlParameter's Value with the first row's value for that column. This practice has zero added value over simply reading the resultset yourself - it's just there for compatibility.
To sum it up, I'd suggest you read the refcursors with your reader and then fetch their results as appropriate.
I am a rookie/newbie in the postgres data access api. I have worked a bit on oracle, sql server and trying to do what i have done with those dbms
The use is very simple
1) a stored procedure aka function with input params
2) Returning or more ref cursors
3) Using an ent lib wrapper to use the npgsql provider/database with it
4) Doing a data adapter fill and running into the issue with some cursor de-referencing.. it appears though i am inside a tran..
5) I just want to get some simple working sample with the latest npgsql provider..
Here is my function
CREATE OR REPLACE FUNCTION public.geterrorcategories(
v_organizationid integer)
RETURNS refcursor
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE cv_1 refcursor;
BEGIN
open cv_1 for
SELECT errorCategoryId, name, bitFlag
FROM ErrorCategories
ORDER BY name;
RETURN cv_1;
END;
$BODY$;
The code using the enterprise lib api/wrapper is as follows.
/// <summary>
/// Executes GetErrorCategories in case of SQL Server or GetErrorCategories for Oracle
/// </summary>
public static DataTable GetErrorCategoriesAsDataTable(string dbKey ,int? ORGANIZATIONID)
{
DataTable tbl = new DataTable();
Database db = Helper.GetDatabase(dbKey);
using (DbConnection con = db.CreateConnection()){
con.Open();
var tran = con.BeginTransaction();
using (DbCommand cmd = con.CreateCommand()){
cmd.Transaction = tran;
BuildGetErrorCategoriesCommand(db, cmd ,ORGANIZATIONID);
cmd.CommandText = "GetErrorCategories";
try {
Helper.FillDataTable(tbl, db, cmd);
con.Close();
} catch (DALException ) {
throw;
}
}
}
return tbl;
}
The command is built as follows.
private static void BuildGetErrorCategoriesCommand(Database db, DbCommand cmd ,int? ORGANIZATIONID){
Helper.InitializeCommand(cmd, 300, "GetErrorCategories");
db.AddReturnValueParameter(cmd);
db.AddInParameter(cmd, "organizationId", DbType.Int32, ORGANIZATIONID);
db.AddCursorOutParameter(cmd, "CV_1");
}
I am not getting any error. I get only 1 row back which i think is this un_named_portal_1 or something but not the results from my table which my query returns
It is frustrating as i would like to keep my application code the same as much as possible but would like to switch providers at run time. I am using a tweaked 'ent lib' contribution database that was created for npgsql.
Hope this helps to point me to the right areas to look for..
There is absolutely no reason above to declare your PostgreSQL function to return a cursor - you can simply return a table, see the PostgreSQL docs for more info.
Npgsql originally had a feature where it automatically "dereferenced" cursors returned from functions, but this has been removed. For more information about this see this issue (warning, it's long...). Some people are requesting that the feature be returned.
I would like to call the DB_ID function of SQL Server to retrieve the databaseID of a user database from scala..
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver")
val connection: Connection = DriverManager.getConnection(jdbcConnectionString)
//SELECT database_id FROM sys.databases WHERE Name
val statement: CallableStatement = connection.prepareCall("{? =call DB_ID(?)}")
statement.registerOutParameter(1,java.sql.Types.INTEGER)
statement.setString(2,s"'ABC_STORE'")
statement.execute()
val a = statement.getInt(1)
I get an error COULD NOT FIND the stored procedure DB_ID.
How do i get this to work.
If you make statement.setString you don't need to use your String between the two '' so change :
statement.setString(2,s"'ABC_STORE'")
by
statement.setString(2, "ABC_STORE")
What the s do in 2,s"' make sure to remove it.
You can learn more here :
Using a Stored Procedure with a Return Status and Prepared Statement doc
I am using SQL Server 2016.
I have a stored procedure GET_RECORDS that takes input parameters for filter and outputs a CURSOR parameter
I want to get this cursor in my SSIS package
I had created data flow task, OleDb source and variables for parameter values. Then mapped parameters
Params mapping screen
but when I wanted to save the component - I got an error
error screen
I tried to add clause WITH RESULT SETS with some dummy columns, but my procedure doesn't return any result set
What am I doing wrong?
Any advices will be helpful.
Thank you.
With regards, Yuriy.
The source component is trying to determine what columns and types will be returned. Because you are using dynamic SQL the metadata can change each time you run it.
With result sets allows you to define the data being returned but should only be used if you are guaranteed to have those results every time you execute.
EDIT:
I create a connection and run the command so that it populates a data table. Then I put the column headers into a string array. There are plenty of examples out there.
Then I use the following function to create a destination table. Finally I create a datareader and pass that to the .Net SqlBulkCopy. Hope this helps.
private void CreateTable(string TableName, string[] Fields)
{
if (TableExists(TableName) && Overwrite)
{
SqlCommand = new SqlCommand($"Drop Table [{TableName}]", SqlConnection);
SqlCommand.ExecuteNonQuery();
}
string Sql = $"Create Table [{TableName}] (";
int ColumnNumber = 1;
foreach (string Field in Fields)
{
string FieldValue = Field;
if (! HasHeaders)
{
FieldValue = "Column" + ColumnNumber;
ColumnNumber++;
}
Sql += $"[{FieldValue}] Varchar(8000),";
}
Sql = Sql + "ImportFileID Int, ID Int Identity(1,1) Not Null, Constraint [PK_" + TableName + "] Primary Key Clustered ([ID] Asc))";
SqlCommand = new SqlCommand(Sql, SqlConnection);
SqlCommand.ExecuteNonQuery();
}
Use ado.net source instead of oledb source, define a simple select and get the columns you wish to return. Now you can define expresión in the dataflow properties.
Search ado.net source dynamic sql
:)
try to return the records and use foreach in ETL instead of cursor
https://www.simple-talk.com/sql/ssis/implementing-foreach-looping-logic-in-ssis/
I think you can do it from a simple way, but I don't know what you are you doing, exactly...
I have the following SQL Server 2012 query:
var sql = #"Select question.QuestionUId
FROM Objective,
ObjectiveDetail,
ObjectiveTopic,
Problem,
Question
where objective.examId = 1
and objective.objectiveId = objectiveDetail.objectiveId
and objectiveDetail.ObjectiveDetailId = ObjectiveTopic.ObjectiveDetailId
and objectiveTopic.SubTopicId = Problem.SubTopicId
and problem.ProblemId = question.ProblemId";
var a = db.Database.SqlQuery<string>(sql).ToList();
Can someone help explain to me if it would be a good idea to put this into a
stored procedure and if so then how could I do that and then call it from my C# code. It was
suggested to me that if it is in a stored procedure then it would run more
efficiently as it would not be recompiled often. Is that the case?
Yes, there is. For starters, a stored procedure is precompiled and stored within your database. Being precompiled, the database engine can execute it more efficiently, since no on-the-fly compilation necessary. Also, database optimizations can be added to support a precompiled procedure. A stored procedure also allows business logic to be encapsulated within the database.
If you decide to go the stored procedure route, then consider the following:
First of all, you will need to create a stored procedure that encapsulates your existing SQL query.
CREATE PROCEDURE ListQuestionIds
#ExamId int
AS
BEGIN
SELECT Question.QuestionUId
FROM Objective
INNER JOIN ObjectiveDetail
ON ( Objective.objectiveId = ObjectiveDetail.objectiveId )
INNER JOIN ObjectiveTopic
ON ( ObjectiveDetail.ObjectiveDetailId = ObjectiveTopic.ObjectiveDetailId )
INNER JOIN Problem
ON ( ObjectiveTopic.SubTopicId = Problem.SubTopicId )
INNER JOIN Question
ON ( Problem.ProblemId = Question.ProblemId )
WHERE Objective.examId = #ExamId;
END;
Please make sure that the tables called by your procedure (Objective, Problem, etc,) have all of the relevant primary keys and indexes in place to enhance the performance of your query.
Next, you will need to call that stored procedure from within your C# code. One way--but by no means the only way--is to create a connection to your database using the SqlConnection object and then executing your procedure via the SqlCommand object.
I would recommend that you take a look at How to execute a stored procedure within C# program for some on-topic examples. But a simple example of such might look like:
string connectionString = "your_connection_string";
using (var con = new SqlConnection(connectionString))
{
using (var cmd = new SqlCommand("ListQuestionIds", con)) {
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.Add(new SqlParameter("#ExamId", examId))
con.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
// Loop through the returned SqlDataReader object (aka. rdr) and
// then evaluate & process the returned question id value(s) here
}
}
}
}
Please note that this sample code does not (intentionally) include any error handling. I leave that up to you to integrate into your application.
Finally, just as an FYI... many of the more modern ORMs (e.g., Entity Framework, NHibernate, etc.) allow you to execute stored procedure-like queries from your C# code without requiring an explicit stored procedure. If you are already using an ORM in your application, then you may want to forgo the stored procedure altogether. Whatever you decide to do, a little research on your end will help you make an informed decision.
I hope this helps you get started. Good luck.