In traditional sql we can chain expression according to if statements.
for example lets say I have variable called "firstName" and I want to get from database all users according to the value in this variable(if empty get all users)
so I will chain the sql string like that
string sql="";
if(firstname!="")
sql=String.format(" And firstname='{0}',firstName)
.ExecuteReader(System.Data.CommandType.Text,"select * from users where 1=1" + sql)
Is there a way to copy this Technique to linq expression?
something like
from U in user
where 1=1 & sql
select U
Change to method syntax instead of query syntax, and chaining is easy.
var query = user.Select(u => u);
if(firstname!="")
query = query.Where(u => u.firstname = firstname);
queries in query syntax are converted at compile-time, so there's not a mechanism to "inject" sql at run time using query syntax.
Related
How to Convert this sql query to Linq.
select sum(OutstandingAmt)from IvfReceiptDetails where IvfReceiptId IN(select IvfReceiptId from IvfReceipts where PatientId = 'SI-49650')
I think it is easier to translate SQL using query comprehension syntax instead of lambda syntax.
General rules:
Translate inner queries into separate query variables
Translate SQL phrases in LINQ phrase order
Use table aliases as range variables, or if none, create range variables from table names
Translate IN to Contains
Translate SQL functions such as DISTINCT or SUM into function calls on the entire query.
Here is the code:
var IvfReceiptIds = from IvfReceipt in IvfReceipts
where IvfReceipt.PatientId = "SI-49650"
select IvfReceipt.IvfReceiptId;
var OutstandingAmtSum = (from IvfReceiptDetail in IvfReceiptDetails
where IvfReciptIds.Contains(IvfReceiptDetail.IvfReceiptId)
select IvfReceiptDetail.OutstandingAmt).Sum();
Try this, First get all IvfReceiptId in array based on your inner query used in where condition then check contains. Change name of your _context if it's different.
var arrIvfReceiptId = _context.IvfReceiptDetails.Where(p=>p.PatientId == "SI-49650").ToArray();
var sum = (from ird in _context.IvfReceiptDetails.Where(p=> arrIvfReceiptId.Contains(p.IvfReceiptId))
select OutstandingAmt).Sum();
Consider the following statements. The first one is a LINQ statement, and the second one is old fashioned SQL. They both produce the correct result. The LINQ statement takes 42 seconds because it doesn’t pass the where clause to Oracle. Oracle has to do a complete table scan, then the where clause is satisfied by LINQ after the result. In contrast, the SQL passes the where clause to Oracle, and takes about 3 seconds to run.
Why doesn’t LINQ pass the where clause to Oracle? What can I do about this?
LINQ:
var SamDlvryGrps3 = (from x in _entities.VW_QCRPT_SAMPLE_DLVRY_GRP_SITE
where x.SAMPLEDELIVERYGROUP == EnteredsmplDlvryGrp
select new BatchIdModView
{
BatchId = x.BATCHID,
sampleDeliveryGroup = x.SAMPLEDELIVERYGROUP
}).Distinct().ToList();
SQL:
string sql = "select distinct BatchId, sampleDeliveryGroup from VW_QCRPT_SAMPLE_DLVRY_GRP_SITE where SAMPLEDELIVERYGROUP = :1";
List<BatchIdModView> SamDlvryGrps = _entities.Database.SqlQuery<BatchIdModView>
(sql, new OracleParameter("#smplDlvryGrp", EnteredsmplDlvryGrp.ToUpper())).ToList();
I am trying to query query the current month, here is my query:
$clients = $this->Clients;
$query = $clients->find();
if($this->Auth->user('role') !== 'admin'){
$query->where(['user_id =' => $this->Auth->user('id')]);
$query->where(['MONTH(dob) = ' => 'EXTRACT(month FROM (NOW()))']);
$query->order(['dob' => 'ASC']);
}
It returns 0 records (my field is a date type), however this query in phpmyadmin works:
SELECT * FROM `clients` WHERE MONTH(dob) = EXTRACT(month FROM (NOW()))
What am I doing wrong?
Just look at the actual generated query (check out your DBMS query log, or try DebugKit), it will look different, as the right hand side value in a key => value condition set is subject to parameter-binding/casting/quoting/escaping. In your case it will be treated as a string, so the condition will finally look something like:
WHERE MONTH(dob) = 'EXTRACT(month FROM (NOW()))'
That will of course not match anything.
You could pass the whole SQL snippet as a single array value, or as an expression object, that way it would be inserted into the query as is (do not insert user values that way, that would create an SQL injection vulnerability!), but I'd suggest to use portable function expressions instead.
CakePHP ships with functions expressions for EXTRACT and NOW, so you can simply do something like:
use Cake\Database\Expression\IdentifierExpression;
use Cake\Database\Expression\QueryExpression;
use Cake\ORM\Query;
// ...
$query->where(function (QueryExpression $exp, Query $query) {
return $exp->eq(
$query->func()->extract('MONTH', new IdentifierExpression('dob')),
$query->func()->extract('MONTH', $query->func()->now())
);
});
Looks a bit complicated, but it's worth it, it's cross DBMS portable as well as auto-quoting compatible. The generated SQL will look something like
WHERE EXTRACT(MONTH FROM (dob)) = (EXTRACT(MONTH FROM (NOW())))
See also
Cookbook > Database Access & ORM > Query Builder > Advanced Conditions
Cookbook > Database Access & ORM > Query Builder > Using SQL Functions
API > \Cake\Database\Expression\QueryExpression::eq()
API > \Cake\Database\FunctionsBuilder::extract()
API > \Cake\Database\FunctionsBuilder::now()
Let's suppose I have a table: Person(Name: univarchar) and this table contains a row "abc".
I search Person by using Hibernate (Criteria API and HQL):
Criteria API:
Criteria c = session.createCriteria(Person.class);
c.add(Restrictions.ilike(name,"abc"));
return c.list();
HQL:
String query = "from Person where lower(name) like :name";
Query q = session.createQuery(query);
query.setString("name","abc");
return query.list();
It return empty result. However, when I use Interactive SQL of Sybase to execute SQL statement that is generated by Hibernate, it return a row "abc".
I found a solution for HQL case. This is to use rtrim function:
String query = "from Person where lower(rtrim(name)) like :name";
...
But my problem is I want to use Criteria API and I cannot find any ways to trim name column by using Criteria API.
Thanks and sorry for my poor English.
Have you tried with this code :
Criteria c = session.createCriteria(Person.class);
c.add(Restrictions.ilike(name,"abc",MatchMode.ANYWHERE));
return c.list();
If this will not work then Read this. Its similar Just he wants to trim while Order you want to trim while Restrictions.
I was trying to figure out how can I set multiple parameters for the IN clause in my SQL query using PreparedStatement.
For example in this SQL statement, I'll be having indefinite number of ?.
select * from ifs_db where img_hub = ? and country IN (multiple ?)
I've read about this in
PreparedStatement IN clause alternatives?
However I can't figure it out how to apply it to my SQL statement above.
There's not a standard way to handle this.
In SQL Server, you can use a table-valued parameter in a stored procedure and pass the countries in a table and use it in a join.
I've also seen cases where a comma-separated list is passed in and then parsed into a table by a function and then used in a join.
If your countries are standard ISO codes in a delimited list like '#US#UK#DE#NL#', you can use a rather simplistic construct like:
select * from ifs_db where img_hub = ? and ? LIKE '%#' + country + '#%'
Sormula will work for any data type (even custom types). This example uses int's for simplicity.
ArrayList<Integer> partNumbers = new ArrayList<Integer>();
partNumbers.add(999);
partNumbers.add(777);
partNumbers.add(1234);
// set up
Database database = new Database(getConnection());
Table<Inventory> inventoryTable = database.getTable(Inventory.class);
ArrayListSelectOperation<Inventory> operation =
new ArrayListSelectOperation<Inventory>(inventoryTable, "partNumberIn");
// show results
for (Inventory inventory: operation.selectAll(partNumbers))
System.out.println(inventory.getPartNumber());
You could use setArray method as mentioned in the javadoc below:
http://docs.oracle.com/javase/6/docs/api/java/sql/PreparedStatement.html#setArray(int, java.sql.Array)
Code:
PreparedStatement statement = connection.prepareStatement("Select * from test where field in (?)");
Array array = statement.getConnection().createArrayOf("VARCHAR", new Object[]{"AA1", "BB2","CC3"});
statement.setArray(1, array);
ResultSet rs = statement.executeQuery();