I am trying to follow the examples in sqlboiler (https://github.com/volatiletech/sqlboiler). But couldn't find a way to get just the columns queried in the select statement?
users, err := models.Users(
Select("id", "name"),
Where("age > ?", 30),
).All(ctx, db)
In this example, .All returns entire tuple containing empty/nil values of columns not queried. I was wondering if there is a way to return a map/list (or any relevant data structure/format) of just the queried columns. Thanks!
You get all the fields, because you get instances of models.User, which have all the fields, you want them or not.
One thing you can do is write your own cut-down User struct, and bind to that.
type LiteUser struct {
ID int `boil:"id"`
Name string `boil:"name"`
}
var users []*LiteUser
err := models.Users(
Select("id", "name"),
Where("age > ?", 30),
).Bind(ctx, db, &users)
Related
I want to convert an SQL query into a JSONiq Query, is there already an implementation for this, if not, what do I need to know to be able to create a program that can do this ?
I am not aware of an implementation, however, it is technically feasible and straightforward. JSONiq has 90% of its DNA coming from XQuery, which itself was partly designed by people involved in SQL as well.
From a data model perspective, a table is mapped to a collection and each row of the table is mapped to a flat JSON object, i.e., all fields are atomic values, like so:
{
"Name" : "Turing",
"First" : "Alan",
"Job" : "Inventor"
}
Then, the mapping is done by converting SELECT-FROM-WHERE queries to FLWOR expressions, which provide a superset of SQL's functionality.
For example:
SELECT Name, First
FROM people
WHERE Job = "Inventor"
Can be mapped to:
for $person in collection("people")
where $person.job eq "Inventor"
return project($person, ("Name", "First"))
More complicated queries can also be mapped quite straight-forwardly:
SELECT Name, COUNT(*)
FROM people
WHERE Job = "Inventor"
GROUP BY Name
HAVING COUNT(*) >= 2
to:
for $person in collection("people")
where $person.job eq "Inventor"
group by $name := $person.name
where count($person) ge 2
return {
name: $name,
count: count($person)
}
Actually, if for had been called from and return had been called select, and if these keywords were written uppercase, the syntax of JSONiq would be very similar to that of SQL: it's only cosmetics.
For example we have model TableRow - columns (:account_number, :month, :department, :phone_number). And have a method that returns filtered rows by arrays of this params.
For required params we can use
TableRow.where('account_number IN (?)', param)
Is there best way to add in this query unrequired params (department, phone_number) that can be nill and we should return records with any params in this column?
There are a couple ways to approach this. If you want your query to be static, you can check the literal value of your param with the SQL logic itself:
TableRow.where('COALESCE(:depts) IS NULL OR department IN (:depts)', depts: param)
You can also build up your relation incrementally in Ruby:
relation = TableRow.all
relation = relation.where(department: depts) if depts.present?
Your question is hard to understand, but if what you want is to filter by phone_number while still retrieving records where phone_number is null, you just have to that:
TableRow.where('phone_number IN (?)', param << nil)
I'm trying to do native SQL in Doctrine. Basically I have 2 parameters:
CANDIDATE_ID - user for who we delete entries,
list of FILE_ID to keep
So I make
$this->getEntityManager()->getConnection()->
executeUpdate( "DELETE FROM FILE WHERE CANDIDATE_ID = :ID AND NOT ID IN :KEEPID",
array(
"ID" => $candidate->id,
"KEEPID" => array(2) )
);
But Doctrine fails:
Notice: Array to string conversion in D:\xampp\htdocs\azk\vendor\doctrine\dbal\lib\Doctrine\DBAL\Connection.php on line 786
Is this bug in Doctrine? I'm making somewhere else select with IN but with QueryBuilder and it's working. Maybe someone could suggest better way of deleting entries, with QueryBuilder for example?
$stmt = $conn->executeQuery('SELECT * FROM articles WHERE id IN (?)',
array(array(1, 2, 3, 4, 5, 6)),
array(\Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
);
From Doctrine's documentation.
You can't pass an array of IDs to a parameter. You can do this for scalar values, but even if this had a 'toString', it wouldn't be what you want.
String concatenation is one method,
"DELETE FROM FILE WHERE CANDIDATE_ID = :ID AND NOT ID IN (". implode(",", $list_of_ids) .")"
But this method goes straight around parameters, and therefore suffers in terms of readability, and is limited to a certain maximum line length, which can vary between databases.
Another approach is to write a function returning a table result, which takes a string of IDs as a parameter.
You could also solve this with a join to a table containing the IDs to keep.
It's a problem I've seen many times with few good answers, but it's usually caused by a misunderstanding in the way the database is modelled. This is a 'code smell' for database access.
Using the database/sql package and drivers for Postgres and Mysql I want to achieve the following. I want to be able to Select one row and know that there is either zero rows, one row, or more than one row. the QueryRow function does not achieve that, because as far as I can ascertain, it will return one row without error regardless of if there is more than one row. For my situation, more than one row may be an error, and I want to know about it. I want to create a general function to do this.I looked at creating a function that uses the Query function, but I do not know how to return the first row if there is more than one row. I want to return the fact that there is more than one row, but I also want to return the first row. To determine that there is more than one row, I have to do a Next, and that overwrites the first row. Obviously I can achieve this without creating a general function, but I want a function to do it because I need to do this in a number of placesCould someone please explain to me how to achieve this. IE. To return the first row from a function when a successful Next has been done or the Next returned nothing.
I'm using both database/sql & MySQLDriver to achieve this. You can download MySQLDriver at https://github.com/go-sql-driver/ .
I wrote execQuery function myself to get one or more rows from database. It's based on MySQL but I think it can also used to Postgres with similar implement.
Assume you have a DB table named test, and have rows named id, name, age.
Code:
var db *sql.DB // it should be initialized by "sql.Open()"
func execQuery(SQL string, args ...interface{}) (rows *sql.Rows, is_succeed bool) {
rows, err := db.Query(SQL, args...)
var ret bool
if err == nil && rows != nil { // if DB query error rows will be nil, it will return false
ret = true
} else {
ret = false
}
return rows, ret
}
Usage:
var name, age string
rows, is_succeed = execQuery("SELECT `name`, `age` FROM `test` WHERE `id` = ?", "123")
if !is_succeed {
// error
return
}
for rows.Next() { // if have zero result rows, this for route won't execute
err := rows.Scan(&name, &age)
// check if has error & do something
}
If you want to know how much rows returned, just add a counter in for route, use SQL can also achieve this.
sql.Rows likes a list structure, rows *sql.Rows points on first row of returned rows. Use rows.Next() to traverse every rows. I think that's what you've asked.
If you really want to know rows count very often, using a cache mechanic like memcacheDB or Redis or just implement a simple counter yourself can help you solve the problem.
I'm attemping to do a simple check for an empty collection in an NHIbernate Query. Here's my code:
var query = QueryNotDeleted().Where(x=>x.Markets.Count() > 0);
QueryNotDeleted returns an IQueryOver. The above line throws an error (Unrecognised method call in epression x.Markets.Count()) because it doesn't recognize the Count() in the query.
I tried
var query = QueryNotDeleted().Where(x=>x.Markets != null);
But unfortunately, Markets is never NULL, so I have to test for a count instead of it being null to get the records I want.
How can I get this "count" syntax correct so that it excludes records where the Markets property is empty?
I was able to get it to work using:
query.RootCriteria.CreateAlias("Markets", "m", JoinType.LeftOuterJoin);
and then
query.RootCriteria.Add(Restrictions.IsNotNull("m.Id"));
If I understand your question correctly you want to get a list of records that don't have corresponding children?
If I wanted to get a list of Orders that have no OrderItems using QueryOver then I would do something like:-
var orders = session.QueryOver<Order>()
.Left.JoinQueryOver(w => w.Items)
.Where(w => w.Order.Id == null);
If this is not the right answer then please can you submit the SQL you are trying to run and the parent/children mappings/.