Azure SQL query slow performance

Azure SQL Intermittently slow at intervals

If you do not have any maintenance job scheduled on the database, then you will need to run some maintenance queries to update the stats if your data in the database is having frequent inserts and updates. Here is  how you can do it as below

Connect to your database from SSMS (SQL Server Management Studio), or another client of your choosing.

Update all your tables data distribution statistics, with a 100% sampling rate (Fullscan). This data is used by the query optimizer to choose an execution plan for the queries, and it’s vital that they are updated to get effective execution plans.

---------------------------Update statistics of all database tables
DECLARE @sql nvarchar(MAX);
SELECT @sql = (SELECT 'UPDATE STATISTICS ' + DB_NAME() + '.' + rtrim(sc.name) + '.' + rtrim(so.name) + ' WITH FULLSCAN, ALL; '
from sys.sysobjects so
join sys.schemas sc
on so.uid = sc.schema_id
where so.xtype = 'U'
               FOR XML PATH(''), TYPE).value('.', 'nvarchar(MAX)');
PRINT @sql
EXEC (@sql)
---------------------------------------------------------------------
Then follow with a recompilation of all objects, by using sp_recompile.

This causes stored procedures, triggers, and user-defined functions to be recompiled the next time that they are run. It does this by dropping the existing plan from the procedure cache forcing a new plan to be created the next time that the procedure or trigger is run. This ensures the new data distribution statistics or indexes are used in execution plans.
----------------------------------------------------------------------
--Force recompilation of all objects

SET QUOTED_IDENTIFIER OFF
DECLARE @sql nvarchar(MAX);
SELECT @sql = (SELECT "EXEC sp_recompile '" + rtrim(sc.name) + "." + rtrim(so.name) + "' "
from sys.sysobjects so
join sys.schemas sc
on so.uid = sc.schema_id
where so.xtype = "U"
               FOR XML PATH(''), TYPE).value('.', 'nvarchar(MAX)');
PRINT @sql
EXEC (@sql)
SET QUOTED_IDENTIFIER ON
----------------------------------------------------------------------
References

UPDATE STATISTICS (Transact-SQL)

https://msdn.microsoft.com/en-us/library/ms187348.aspx

sp_recompile (Transact-SQL)

https://msdn.microsoft.com/en-us/library/ms181647.aspx