I have just started using LinqPad:
var con1 = from con in table
where con.tableKey == Guid.Parse("8EA5DC2C-2603-499A-A9D3-00019B53421F")
select con;
con.Dump();
throws me error
") or end of expression expected (change the Query Language to 'C# Statements' for multi-statement queries)"
Can anyone please correct me?
And also i have notices File-> New Query, New Query same properties on linqpad.
What is the difference between them? Thanks.
Make sure your type of query is C# statements and not C# expression... but if you aren't doing more than 1 statement you don't need the con.Dump(); (I think)
Related
I'm using npgsql as a nuget package in visual studio 2017 with visual basic.
Various commands do work very well but an ExecuteScalar allways returns 'nothing' although it should give a result.
The command looks like this:
Dim ser As Integer
Dim find = New NpgsqlCommand("SELECT serial from dbo.foreigncode WHERE code = '#code';", conn)
Dim fcode = New NpgsqlParameter("code", NpgsqlTypes.NpgsqlDbType.Varchar)
find.Parameters.Add(fcode)
find.Prepare()
fcode.Value = "XYZ"
ser = find.ExecuteScalar() ==> nothing
When the command string is copied as a value during debugging and pasted into the query tool of PGADMIN it delivers the correct result. The row is definitely there.
Different Commands executed with ExecuteNonQuery() work well, including ones performing UPDATE statements on the row in question.
When I look into the properties of the parameter fcode immediately before the ExecuteScalar it shows 'fcode.DataTypeName' caused an exception 'System.NotImplementedException'.
If I change my prepared statement to "SELECT #code" and set the value of the parameter to an arbitrary value just this value is returned. There is no access to the table taking place because the table name is not part of the SELECT in this case. If I remove the WHERE CLAUSE in the SELECT and just select one column, I would also expect that something has to be returned. But again it is nothing.
Yes there is a column named serial. It is of type bigint and can not contain NULL.
A Query shows that there is no single row that contains NULL in any column.
Latest findings:
I queried a different table where the search column and the result column happen to have the same datatype. It works, so syntax, passing of parameter, prepare etc. seems to work in principal.
The System.NotImplementedException in the DataTypeName property of the parameter occurs as well but it works anyway.
I rebuilt the index of the table in question. No change.
Still: when I copy/paste the CommandText and execute it in PGAdmin it shows the correct result.
Modifying the Command and using plain text there without parameter and without prepare still does yield nothing. The plain text CommandText was copy/pasted from PGAdmin where it was successfully executed before.
Very strange.
Reverting search column and result column also gives nothing as a result.
Please try these two alternatives and post back your results:
' Alternative 1: fetch the entire row, see what's returned
Dim dr = find.ExecuteReader()
While (dr.Read())
Console.Write("{0}\t{1} \n", dr[0], dr[1])
End While
' Alternative 2: Check if "ExecuteScalar()" returns something other than an int
Dim result = find.ExecuteScalar()
... and (I just noticed Honeyboy Wilson's response!) ...
Fix your syntax:
' Try this first: remove the single quotes around "#code"!
Dim find = New NpgsqlCommand("SELECT serial from dbo.foreigncode WHERE code = #code;", conn)
Update 1
Please try this:
Dim find = New NpgsqlCommand("SELECT * from dbo.foreigncode;", conn)
Q: Does this return anything?
Dim dr = find.ExecuteReader()
While (dr.Read())
Console.Write("{0}\t{1} \n", dr[0], dr[1])
End While
Q: Does this?
Dim result = find.ExecuteScalar()
Q: Do you happen to have a column named "serial"? What is it's data type? Is it non-null for the row(s) with 'XYZ'?
Please update your original post with this information.
Update 2
You seem to be doing ":everything right":
You've confirmed that you can connect,
You've confirmed that non-query updates to the same table work (with npgsql),
You've confirmed that the SQL queries themselves are valid (by copying/pasting the same SQL into PGAdmin and getting valid results).
As Shay Rojansky said, "System.NotImplementedException in the DataTypeName property" is a known issue stepping through the debugger. It has nothing to do with your problem: https://github.com/npgsql/npgsql/issues/2520
SUGGESTIONS (I'm grasping at straws)::
Double-check "permissions" on your database and your table.
Consider installing a different version of npgsql.
Be sure your code is detecting any/all error returns and exceptions (it sounds like you're probably already doing this, but it never hurts to ask)
... and ...
Enable verbose logging, both client- and server-side:
https://www.npgsql.org/doc/logging.html
https://www.postgresql.org/docs/9.0/runtime-config-logging.html
... Finally ...
Q: Can you make ANY query, from ANY table, using ANY query method (ExecuteReader(), ExecuteScalar(), ... ANYTHING) from your npgsql/.Net client AT ALL?
I finally found it. It's often the small things that can have a big impact.
When the value was assigned to the parameter a substring index was incorect.
Now it works perfectly.
Thanks to everybody who spent his time on this.
I have SQL query, where I have two parameters and one output parameter (varchar).
How I should call the procedure and get the output parameter?
Thanks.
First of all you have to connect to your db. What technology are you using?
In any case it could be something like that (code is written for c# & Oracle, but it will give you an idea how to solve your case):
IDbConnection dbConnection = new OracleConnection(your_connectionstring)
var param = new OracleDyamicParameters();
param.Add("out_result", OracleDbType.Int64, ParameterDirection.Output);
string query = "Your_proc_Name";
await SqlMapper.QueryAsync<MyReturnClass>(dbConnection, query, param: param, commandType: CommandType.StoredProcedure);
db_res.Result = param.GetOutResult();
I'm in the process of writing an update code to update user information on an asset used for a project I have. The code is below...
AlteredUser = dbContext.Assets.Where(c >= c.ParentAssetID = ParentAssetId And c.AssetDecription = "USER").SingleOrDefault()
AlteredUser.AssetName = UserName
dbContext.SubmitChanges()
I'm getting an error message saying " 'c' is not declared ". I've seen several examples of how to use the where clause within dbContext, and all of them use a letter as LINQ normally does. I cannot figure out why it is erroring out for me.
Any help would be greatly appreciated.
Thank you!
>= is a comparison operator.
To create a lambda in VB, write
Function(c) c....
my problem is about this kind of query :
select * from SOMETABLE where SOMEFIELD in ('STRING1','STRING2');
the previous code works fine within Sql Developer.
The same static query also works fine and returns me a few results;
Query nativeQuery = em.createNativeQuery(thePreviousQuery,new someResultSet());
return nativeQuery.getResultList();
But when I try to parameterize this, I encounter a problem.
final String parameterizedQuery = "select * from SOMETABLE where SOMEFIELD in (?selectedValues)";
Query nativeQuery = em.createNativeQuery(parameterizedQuery ,new someResultSet());
nativeQuery.setParameter("selectedValues","'STRING1','STRING2'");
return nativeQuery.getResultList();
I got no result (but no error in console).
And when I look at the log, I see such a thing :
select * from SOMETABLE where SOMEFIELD in (?)
bind => [STRING1,STRING2]
I also tried to use no quotes (with similar result), or non ordered parameter (:selectedValues), which leads to such an error :
SQL Error: Missing IN or OUT parameter at index:: 1
I enventually tried to had the parentheses set directly in the parameter, instead of the query, but this didn't work either...
I could build my query at runtime, to match the first (working) case, but I'd rather do it the proper way; thus, if anyone has an idea, I'll read them with great interest!
FYI :
JPA version 1.0
Oracle 11G
JPA support the use of a collection as a list literal parameter only in JPQL queries, not in native queries. Some JPA providers support it as a proprietary feature, but it's not part of the JPA specification (see https://stackoverflow.com/a/3145275/1285097).
Named parameters in native queries also aren't part of the JPA specification. Their behavior depends on the persistence provider and/or the JDBC driver.
Hibernate with the JDBC driver for Oracle support both of these features.
List<String> selectedValues = Arrays.asList("STRING1", "STRING2");
final String parameterizedQuery = "select * from SOMETABLE where SOMEFIELD in (:selectedValues)";
return em.createNativeQuery(parameterizedQuery)
.setParameter("selectedValues", selectedValues)
.getResultList();
Instead of:
nativeQuery.setParameter("selectedValues", params);
I had to use:
nativeQuery.setParameterList("selectedValues", params);
This worked for me in derby. parameter without "()".
List<String> selectedValues = Arrays.asList("STRING1", "STRING2");
final String parameterizedQuery = "select * from SOMETABLE where SOMEFIELD in
:selectedValues";
return em.createNativeQuery(parameterizedQuery)
.setParameter("selectedValues", selectedValues)
.getResultList();
Replace this:
nativeQuery.setParameter("selectedValues","'STRING1','STRING2'");
with
List<String> params;
nativeQuery.setParameter("selectedValues",params);
I also faced the same issue.
This is what I did:
List<String> sample = new ArrayList<String>();
sample.add("sample1");
sample.add("sample2");
And now you, can set the sample in params.
I am trying to send a SQL prepared statement to MySQL DB. This is what I have:
String sql1 = "SELECT idReimbursed_Funds As idReimFunds FROM reimbursedfunds Where ReimFundsName = ? AND Date = ?";
PreparedStatement pstmt1 = conn.prepareStatement(sql1);
pstmt1.setString(1, reimfund.getReimFundsName());
pstmt1.setDate(2, (Date) reimfund.getDate());
ResultSet rs1 = pstmt1.executeQuery(sql1);
while(rs1.next()){
idReimFunds = rs1.getInt("idReimFunds");
}
After googling this problem, I found solutions to use parenthesis around the question marks or the whole where clause such as:
String sql1 = "SELECT idReimbursed_Funds As idReimFunds FROM reimbursedfunds Where (ReimFundsName = ?) AND (Date = ?)";
This didn't work though. I get the same error message that is generated by my original code:
"You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?) AND (Date = ?)' at line 1.
When I try the SQL statement in MySQL Workbench is works fine. Is there a way to use 2 where clauses with JDBC? I know in other posts people have answered that it has to be sent as two different queries, but I thought I would ask just in case someone else reads this posts and knows of a way. Thank you!
The problem (apart from the Date issue as mentioned by bgp), is the line:
ResultSet rs1 = pstmt1.executeQuery(sql1);
You are trying to execute a query string on a prepared statement, which is not allowed by the JDBC standard (MySQL should actually throw an exception instead of sending it to the server as it currently does, but the end result is the same). The documentation of Statement.executeQuery(String sql) says:
Throws:
SQLException - if a database access error occurs, this method is called on a closed Statement, the given SQL statement produces anything other than a single ResultSet object, the method is called on a PreparedStatement or CallableStatement
(emphasis mine)
The reason is that you want to execute the prepared statement, not any other query. You should call PreparedStatement.executeQuery() (so without a parameter):
ResultSet rs1 = pstmt1.executeQuery();
Pretty sure this is because "Date" is a MySQL keyword (reserved). Call the field something else or escape it with backticks, i.e. `Date`