I have two models Reference and Product, Reference has many Product and I need to run the next query (with some Loopback's method) so I doesn't get the empty products.
SELECT DISTINCT R.id
FROM Reference R
WHERE EXISTS (
SELECT id FROM Product P
WHERE P.referenceId = R.id AND P.stock > 0
)
Thanks!
Currently is not posible to query a model filtering based on a related model property using the built-in methods/query language, check this issue. So you will have to execute your sql using the datasource connector. That is for example if you have a model file called Reference.js:
var dbConnection = Reference.dataSource.connector;
dbConnection.execute(yourSql, [], function (err, references) {});
The result will be an array of objects with only the id property. Check this
Another option could be do the relation bidirectional (Product belongs to Reference) and query for products having stock > 0, but you are going to have to group the repeated values:
var Product = Reference.app.models.Product;
Product.find({where: {stock: {gt:0}}, fields: {referenceId:true}}, function (err, prods) {})
Related
I have the following query trying to get count of a query:
var testQuery = Db
.From<Blog>()
.LeftJoin<BlogToBlogCategory>()
.Where(x => x.IsDeleted == false)
.OrderBy(x => x.ConvertedPrice);
var testCount = Db.Scalar<int>(testQuery.Select<Blog>(x => Sql.CountDistinct(x.Id)));
var results = Db.LoadSelect(testQuery.SelectDistinct());
It gives error:
42803: column "blog.converted_price" must appear in the GROUP BY clause or be used in an aggregate function
Issue seems to be the orderby statement. If I remove it then the error goes away. Why does this stop count distinct working?
I am having to clear orderby on all queries I do like this. Is it supposed to work this way?
Also I just realised count is wrong. Results is 501 unique records and testCount is 538.
What am I doing wrong?
Whenever in doubt with what an OrmLite query is generating, you can use the BeforeExecFilter to inspect the DB command before its executed or to just output the query to the Console you can use:
OrmLiteUtils.PrintSql();
You shouldn't be using OrderBy with aggregate scalar functions like COUNT which is meaningless and will fail in your case because it needs to included the GROUP BY clause for joined table queries.
Your specifically querying for COUNT(DISTINCT Id) if you wanted the row count for the query you can instead use:
var testCount = Db.RowCount(testQuery);
If you wanted to use COUNT(*) instead, you can use:
var testCount = Db.Count(testQuery);
I have a query (Update statement) wrapped in a function and will need to perform the same statement on multiple columns during the course of my script
async function update_percentage_value(value, id){
(async () => {
const client = await pool.connect();
try {
const res = await client.query('UPDATE fixtures SET column_1_percentage = ($1) WHERE id = ($2) RETURNING *', [value, id]);
} finally {
client.release();
}
})().catch(e => console.log(e.stack))
}
I then call this function
update_percentage_value(50, 2);
I have many columns to update at various points of my script, each one needs to be done at the time. I would like to be able to just call the one function, passing the column name, value and id.
My table looks like below
CREATE TABLE fixtures (
ID SERIAL PRIMARY KEY,
home_team VARCHAR,
away_team VARCHAR,
column_1_percentage INTEGER,
column_2_percentage INTEGER,
column_3_percentage INTEGER,
column_4_percentage INTEGER
);
Is it at all possible to do this?
I'm going to post the solution that was advised by Sehrope Sarkuni via the node-postgres GitHub repo. This helped me a lot and works for what I require:
No column names are identifiers and they can't be specified as parameters. They have to be included in the text of the SQL command.
It is possible but you have to build the SQL text with the column names. If you're going to dynamically build SQL you should make sure to escape the components using something like pg-format or use an ORM that handles this type of thing.
So something like:
const format = require('pg-format');
async function updateFixtures(id, column, value) {
const sql = format('UPDATE fixtures SET %I = $1 WHERE id = $2', column);
await pool.query(sql, [value, id]);
}
Also if you're doing multiple updates to the same row back-to-back then you're likely better off with a single UPDATE statement that modifies all the columns rather than separate statements as they'd be both slower and generate more WAL on the server.
To get the column names of the table, you can query the information_schema.columns table which stores the details of column structure of your table, this would help you in framing a dynamic query for updating a specific column based on a specific result.
You can get the column names of the table with the help of following query:
select column_name from information_schema.columns where table_name='fixtures' and table_schema='public';
The above query would give you the list of columns in the table.
Now to update each one for a specific purpose, You can store the result set of column name to a variable and pass that variable to the function to perform the required action.
Using a vanilla CosmosDB collection (all default), adding documents like this:
{
"id": "3",
"name": "Hannah"
}
I would like to retrieve records ordered by id, like this:
SELECT c.id FROM c
ORDER BY c.id
This give me the error Order-by item requires a range index to be defined on the corresponding index path.
I expect this is because /id is hash indexed and not range indexed. I've tried to change the Indexing Policy in various ways, but any change I make which would touch / or /id gets wiped when I save.
How can I retrieve documents ordered by ID?
The best way to do this is to store a duplicate property e.g. id2 that has the same value of id, and is indexed using a range index, then use that for sorting, i.e. query for SELECT * FROM c ORDER BY c.id2.
PS: The reason this is not supported is because id is part of a composite index (which is on partition key and row key; id is the row key part) The Cosmos DB team is working on a change that will allow sorting by id.
EDIT: new collections now support ORDER BY c.id as of 7/12/19
I found this page CosmosDB Indexing Policies , which has the below Note that may be helpful:
Azure Cosmos DB returns an error when a query uses ORDER BY but
doesn't have a Range index against the queried path with the maximum
precision.
Some other information from elsewhere in the document:
Range supports efficient equality queries, range queries (using >, <,
>=, <=, !=), and ORDER BY queries. ORDER By queries by default also require maximum index precision (-1). The data type can be String or
Number.
Some guidance on types of queries assisted by Range queries:
Range Range over /prop/? (or /) can be used to serve the following
queries efficiently:
SELECT FROM collection c WHERE c.prop = "value"
SELECT FROM collection c WHERE c.prop > 5
SELECT FROM collection c ORDER BY c.prop
And a code example from the docs also:
var rangeDefault = new DocumentCollection { Id = "rangeCollection" };
// Override the default policy for strings to Range indexing and "max" (-1) precision
rangeDefault.IndexingPolicy = new IndexingPolicy(new RangeIndex(DataType.String) { Precision = -1 });
await client.CreateDocumentCollectionAsync(UriFactory.CreateDatabaseUri("db"), rangeDefault);
Hope this helps,
J
I've a problem with LINQ. Basically a third party database that I need to connect to is using the now depreciated text field (I can't change this) and I need to execute a distinct clause in my linq on results that contain this field.
I don't want to do a ToList() before executing the Distinct() as that will result in thousands of records coming back from the database that I don't require and will annoy the client as they get charged for bandwidth usage. I only need the first 15 distinct records.
Anyway query is below:
var query = (from s in db.tSearches
join sc in db.tSearchIndexes on s.GUID equals sc.CPSGUID
join a in db.tAttributes on sc.AttributeGUID equals a.GUID
where s.Notes != null && a.Attribute == "Featured"
select new FeaturedVacancy
{
Id = s.GUID,
DateOpened = s.DateOpened,
Notes = s.Notes
});
return query.Distinct().OrderByDescending(x => x.DateOpened);
I know I can do a subquery to do the same thing as above (tSearches contains unique records) but I'd rather a more straightfoward solution if available as I need to change a number of similar queries throughout the code to get this working.
No answers on how to do this so I went with my first suggestion and retrieved the unique records first from tSearch then constructed a subquery with the non unique records and filtered the search results by this subquery. Answer below:
var query = (from s in db.tSearches
where s.DateClosed == null && s.ConfidentialNotes != null
orderby s.DateOpened descending
select new FeaturedVacancy
{
Id = s.GUID,
Notes = s.ConfidentialNotes
});
/* Now filter by our 'Featured' attribute */
var subQuery = from sc in db.tSearchIndexes
join a in db.tAttributes on sc.AttributeGUID equals a.GUID
where a.Attribute == "Featured"
select sc.CPSGUID;
query = query.Where(x => subQuery.Contains(x.Id));
return query;
I want to perform a simple join on two tables (BusinessUnit and UserBusinessUnit), so I can get a list of all BusinessUnits allocated to a given user.
The first attempt works, but there's no override of Select which allows me to restrict the columns returned (I get all columns from both tables):
var db = new KensDB();
SqlQuery query = db.Select
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
The second attept allows the column name restriction, but the generated sql contains pluralised table names (?)
SqlQuery query = new Select( new string[] { BusinessUnitTable.IdColumn, BusinessUnitTable.NameColumn } )
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
Produces...
SELECT [BusinessUnits].[Id], [BusinessUnits].[Name]
FROM [BusinessUnits]
INNER JOIN [UserBusinessUnits]
ON [BusinessUnits].[Id] = [UserBusinessUnits].[BusinessUnitId]
WHERE [BusinessUnits].[RecordStatus] = #0
AND [UserBusinessUnits].[UserId] = #1
So, two questions:
- How do I restrict the columns returned in method 1?
- Why does method 2 pluralise the column names in the generated SQL (and can I get round this?)
I'm using 3.0.0.3...
So far my experience with 3.0.0.3 suggests that this is not possible yet with the query tool, although it is with version 2.
I think the preferred method (so far) with version 3 is to use a linq query with something like:
var busUnits = from b in BusinessUnit.All()
join u in UserBusinessUnit.All() on b.Id equals u.BusinessUnitId
select b;
I ran into the pluralized table names myself, but it was because I'd only re-run one template after making schema changes.
Once I re-ran all the templates, the plural table names went away.
Try re-running all 4 templates and see if that solves it for you.