Extreme query optimization with IN clause and subquery

Extreme query optimization with IN clause and subquery

By : Stephen Sides
Date : November 14 2020, 04:48 PM
around this issue I've found that MySQL tends to perform better with JOIN than correlated subqueries.
code :
SELECT ch1.*
FROM citizens_dynamic AS ch1
JOIN (SELECT id, MAX(update_id_to) AS update_id_to
      FROM citizens_dynamic
      WHERE id IN (4369943, ..., 4383420, 4383700)
      GROUP BY id) AS ch2
    ON ch1.id = ch2.id
WHERE ch1.id IN (4369943, ..., 4383420, 4383700)

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Query optimization: max() in subquery

Query optimization: max() in subquery

By : Sh42
Date : March 29 2020, 07:55 AM
wish helps you MAX always process all rows - use order by and limit - so query will look this way
code :
 SELECT * FROM wbsites WHERE url = '...' ORDER BY id DESC LIMIT 1
Risk-Parity Portfolio Optimization using Extreme Optimization in C#

Risk-Parity Portfolio Optimization using Extreme Optimization in C#

By : SNIPJop_
Date : March 29 2020, 07:55 AM
it should still fix some issue If the objective function computation throws, I strongly recommend that you run the code through the debugger to identify the exact location of the throwing code. My first bet is that the error happens due to vector size mismatch, for example in the matrix-vector multiplication. If you get to the bottom of this error, chances are that the optimization will then run smoothly.
If you want to try alternative algorithms instead, you might want to take a look at one of the following solutions. They all support specification of (non-) linear constraints, and it is not necessary to provide objective function and constraint gradients.
Subquery in Linq query giving A query body must end with a select clause or a group clause

Subquery in Linq query giving A query body must end with a select clause or a group clause

By : hoppjo
Date : March 29 2020, 07:55 AM
will help you The closing round paranthesis ends the query which needs a select at the end.
Why don't you use method syntax? It is much better readable in this case. Also, a Select is optional with .Where and method syntax:
code :
  join d in TourDates on t.TourId equals d.TourId
  where d.Date == dt
  select new
       booked = Bookings.Where(b => d.TourDateId == b.TourDateId)
                        .Sum(b => b.NumberBooked()) 
[Oracle]Optimization a query contain a max subquery

[Oracle]Optimization a query contain a max subquery

By : Alain Parmentier
Date : March 29 2020, 07:55 AM
seems to work fine Use an analytical function (single table scan) rather than a correllated sub-query (two table scans):
code :
SELECT product,
FROM   (
  SELECT product,
         MAX( CASE WHEN quantity_in_stock > 0 THEN price END ) OVER ( PARTITION BY product ) AS max_price_in_stock
  FROM   MyTable
WHERE price = max_price_in_stock;
mysql performance optimization for a subquery in select clause

mysql performance optimization for a subquery in select clause

By : Deividas Brasas
Date : March 29 2020, 07:55 AM
This might help you In almost all cases, MySQL punts when it encounters a "prefix index" (INDEX(..., coords(25)). Specifically, it cannot claim "Using index" since the index is not "covering". That is, it may need bytes after the first 25.
Since idx_providerIdCoords and idx_providerId are identical, you should not expect the Optimizer to use one instead of the other.
code :
KEY `idx_providerId` (`companyId`,`coords`(25)),
KEY `idx_providerIdCoords` (`companyId`,`coords`(25))
PRIMARY KEY(`companyId`,`coords`),
KEY (`id`)
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